Ajay is the founder of GMass and has been developing email sending software for 20 years.
If you’ve used our Google Sheets integration to send your mail merge campaigns, you may have noticed how UGLY our spreadsheet dropdown used to be. If you had lots of spreadsheets, finding the right one was a pain.
No longer! Now, the spreadsheet dropdown is BEAUTIFUL, and you can easily search for the right spreadsheet just by typing a few characters that match any part of the name.
Just type a few characters, and your matching spreadsheets will appear.
In fact, we’ve updated all of the major dropdown menus in GMass to this new style, including the Past Campaigns and the Load Content dropdowns.
The new awesome dropdown for Past Campaigns.
And here’s the improved Load Content dropdown:
The awesome searchable dropdown menu to load a campaign’s content
To get the update, your Chrome browser has to update the GMass extension to the latest version 4.0.1, which will happen in the next 48 hours automatically. Don’t want to wait? You can also manually update the extension immediately by:
1. Going to chrome://extensions and clicking the Update extensions now button at the top.
2. Then reloading Gmail (or Google Inbox) in the browser.
See why GMass has 300k+ users and 7,500+ 5-star reviews
Email marketing. Cold email. Mail merge. Avoid the spam folder. Easy to learn and use. All inside Gmail.
Over the weekend, we updated some of the software components that GMass is built on in preparation for a big feature launch, and in doing so, we updated MimeKit from version 1.12 to the latest release 1.18. That upgrade unfortunately broke some of our email address validation code, and many users saw a “token offset” error as a result.
Here’s what happened. Previously, in version 1.12, the following scenarios would pass without throwing an exception:
MimeKit Code Sample: These scenarios pass, and no exception is thrown.
After updating to version 1.18, the top two of the three scenarios do throw an exception:
MimeKit Code Sample: After updating to version 1.18, these throw a parsing exception.
The impact on GMass is such that if you’re connecting to a Google Sheets spreadsheet, and your column containing email addresses has a bad data value that is an invalid email address, such as “[email protected];[email protected]”, whereas before our code would handle this appropriately and eventually filter the bad entry out, now all of a sudden, our code was throwing an exception.
Making matters more complex was that the MimeKit TryParse didn’t always catch a string that could not be converted into a MimeKit.MailboxAddress object. For example:
MimeKit Code Sample: TryParse returns true, but the string still can’t be converted to a MailboxAddress object.
In the above samples, TryParse returns false for “[email protected];[email protected]” but returns true for “test<[email protected]>”. It returns true for the latter because it assumes that the part outside the angle brackets is the Name, and so Name=test and[email protected]. Our code though attempts to create a MailboxAddress object from the whole string, and in this case, the parse into Name and Address doesn’t happen, as the constructor assumes that the entire string represents just the Address portion of the object.
We did check the Release Notes for MimeKit before deploying the update, but there was nothing indicating the change in email parsing rules. Still however, we are eternally grateful to Jeffrey Stedfast for building and maintaining the MimeKit library for the .NET framework. Without it, my job as a software developer parsing and assembling email messages would be far more difficult.
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Gmail Error: You have reached a limit for sending mail. your message was not sent.
If you’re sending mail merge emails from your Gmail account, you’re likely aware of the basic limits that Gmail and G Suite set for your accounts. Generally, those limits are 500 emails/day for Gmail accounts and 2,000 emails/day for G Suite accounts. As is often the case though, users find that Gmail limits them below the stated values of 500 and 2,000 per day. For example, a new Gmail account can often only send 10-20 emails in its first 24-hour period. Similarly, a new G Suite account, especially when the domain is a new customer of G Suite, also has limits more restrictive than 2,000 emails/day.
Troubleshooting:
If you find that your sending volume is under the stated limits but are still getting the dreaded “You have reached a limit” bounce in Gmail, here are some strategies to help.
G Suite User? Contact G Suite Support
I’ve experienced cases where my own G Suite account was limited to 750 or 1,000 emails per 24 hours rather than 2,000. I contacted support, and they admitted that my account had been mistakenly limited and eventually resolved the issue and allowed me greater sending power. Here’s my correspondence with support:
Correspondence with G Suite support about Gmail limits
Use the “throttle” setting to add a few seconds between emails
On Google’s official page describing Gmail sending limits, the 500 and 2,000 daily limits are mentioned. Anecdotally though, we’ve found that sending too many emails within too short a time span can also cause a limit to kick in. One support agent communicated that too many emails sent within a 10-minute period will set off red flags. Use the GMass throttle setting to add a few seconds in between emails. This will slow down the delivery of your messages, but help avoid any per-minute or per-hour limitations.
G Suite User? Perform an administrative reset
As a G Suite user, you can have your Admin reset your account’s quota if you are getting “You have reached your limit” bounces. However, this can only be done 5x/year.
Reset your Gmail quota if you are a G Suite user
Circumvent Gmail’s servers altogether
You can now use your Gmail account to send mail merge campaigns through any SMTP server, bypassing Gmail’s servers and sending limits. This will allow you to use GMass to send mail merge campaigns through your Gmail account, just like normal, but your emails will be routed through a third-party SMTP service like Sendgrid, Mailgun, or JangoSMTP.
How can you programmatically detect these bounces?
If you’re a software developer building your own mail merge system for Gmail, you may want to know how to write code to detect these “You have reached a limit” bounces. It used to be easy, because Gmail used to send these notifications from a special address, [email protected].
In the summer of 2019, however, Google changed the address to the standard bounce notification address of [email protected], which then made it more difficult to detect “reached a limit” bounces from other types of bounces, like those indicating a bad recipient email address. There is however, one distinguishing factor that separates “reached a limit” bounces from all other kinds of bounces. The “reached a limit” bounce will have a Subject line of “Re: ” plus the original email’s Subject line. All other bounces from the “mailer-daemon” address will have the subject of “Delivery Status Notification (Failure)” or “Delivery Status Notification (Delay)”. For example, if the email you sent had the Subject “Company Newsletter”, and you receive an over-limit bounce, it will have the Subject of “Re: Company Newsletter”.
It’s also worth noting that the message will be in the same language as you’ve set your Gmail settings.
The full English message is:
You have reached a limit for sending mail. Your message was not sent.
The German message is:
Sie haben die Begrenzung zum Senden von E-Mails erreicht. Ihre Nachricht konnte daher nicht gesendet werden.
The Norwegian message is:
Du har nådd grensen for sending av e-post. Meldingen din er ikke sendt.
The Spanish message is:
Has llegado al límite de mensajes que puedes enviar. Tu mensaje no se ha enviado.
Further Reading
If you do find that you’re getting bounces because you’re over your Gmail limit, GMass will re-try sending those emails for you later automatically, but you can also manually re-send to the addresses that bounced.
Email marketing, cold email, and mail merge inside Gmail
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GMass runs on a farm of Windows servers, and as the chief systems administrator, one of the constant worries in the back of my mind is whether any of the disks on any of the servers is near capacity. Naturally, I decided to Google “Windows disk space monitor”.
Given the usefulness of such a tool for any Windows server administrator like myself, I was expecting to be overwhelmed with viable options. Not only was I not overwhelmed, but the first two disk space monitors I downloaded sucked — to the point that I can’t even believe they are on the first page of Google. It goes to show that Google’s search results don’t always yield the best tools, just the most popular. Case in point, GMass is probably the world’s best Gmail mail merge tool, but a search for “Gmail mail merge” and GMass is shown near the bottom of page 1 and sometimes at the top of page 2. Yes, competition for that term is stiff indeed.
But I digress. Googling for “Windows disk space monitor” produces the following tools, and in this order:
Before I explain why 4 out of these 5 suck, let me first explain exactly what I wanted in the right disk space monitoring software:
It should run as a service, so that if the server re-boots itself in the middle of the night, my disk space is still being monitored.
It should have the ability to email me at defined thresholds, either in actual amount of space left or percentage of space left.
That’s all — just two simple requirements that most software calling itself “disk space monitoring” software failed to meet. Let’s break it down.
Windows Performance Logs and Alerts
The options to be alerted include: logging an entry in the Application Event Log, sending a network message to another server, initiating a performance data log, or running an EXE. That’s right — no email option, no text message option. How does Microsoft not understand the importance of email? They bought Hotmail in the late 90s, created Microsoft Exchange as their own email server platform, and now compete head-to-head against Gmail with Outlook.com. Yet the notion that a sysadmin would want to get an email to alert them of impending server doom is somehow lost upon them.
Why it sucks:No option to be emailed.
Netwrix Disk Space Monitor
A simple, and supposedly free tool, that at first glance, I was convinced would solve my problem and my search would be over. Ehhh, not quite. Here’s a screenshot of the email settings. Let’s see if you can figure out what’s missing:
On the surface, it looks like it has everything you need to have an email sent to yourself when there’s a disk space issue. SMTP server, recipient address, From address. But wait…there’s no place to input SMTP server login information. Pretty much every SMTP server in the universe requires authentication by username and password (a few still let you authenticate by IP address), but given that there’s a thing called “spam” nowadays, Netwrix’s tool would only work circa 1999, when most SMTP servers were still open relays.
Why it sucks:No option to authenticate into the SMTP server.
Disk Monitor Lite
Total misnomer. Does some cool stuff and generates a cool report, but it doesn’t actually do any monitoring. That’s right — while it can generate on-demand reports, if you look at its feature list, nowhere will you find the ability to be alerted upon low disk space.
Why it sucks:No actual monitoring.
Paessler PRTG Network Monitor
I’m betting that this tool would have done exactly what I wanted, but figuring out how to get it to do it was a hurdle I was unwilling to cross. This tool does a lot. And as such, it’s UI is complex. All I cared about was knowing when my disks were about to fill up, and this tool does 1,000 things more. Along with installing three different applications (the Network Monitor, the Administration Tool, and the Enterprise Console) to your Windows Start menu, there are at least two different user interfaces to manage.
Here’s what I saw when I first installed and launched the tool:
And here is the Enterprise Console.
Do you see any prompts that ask at what disk space threshold I want to be alerted? Neither do I. Next.
Why it sucks: It probably doesn’t, but it’s complicated as hell.
Meerkat
At the bottom of page 1 of the Google search results was a little tool called Meerkat. I liked that it was called “meerkat”, and I liked that it was created and explained by a sole developer. And obviously, I liked that it was free. Let’s go right to a screenshot:
Meerkat Disk Space Monitor “Disks” settings
Nice. It shows me my disks, let me check the ones to monitor, and set the free space threshold to be alerted.
Meerkat Disk Space Monitor “Options”
And look at that…right below the space where I set my SMTP server, I set my SMTP server username and password. Beautiful. I think I have a winner, until I go to my second server to install it. The install fails because I have .NET 4.7 installed (the latest), and it ONLY works with 3.5:
Meerkat won’t install unless you have exactly .NET 3.5 installed.
Why it sucks: It requires a very specific .NET version, 3.5, to run. If you have anything greater, like version 4.7, which is the latest right now, it won’t install.
Advanced Disk Space Monitor (the WINNER)
You have to go to page 2 of the search results to find the one tool that doesn’t suck. It doesn’t suck because it lets you define your thresholds for each disk individually. It doesn’t suck because it will email you an alert when you’re running out of space.
The general disk space settings for Advanced Disk Space Monitor
It doesn’t suck because it lets you configure a username and password for the SMTP server through which the email is sent. And finally, it doesn’t suck, because it will actually run on a Windows server with the latest .NET framework installed. Beautiful. We have a winner. It will, however, cost you $20 per license. But after all the effort I’ve put in so far, $100 for five servers is nothing.
The email settings for Advanced Disk Space Monitor
Why it sucks:It doesn’t! It’s awesome.
One more option
After I found my winner, I stopped my search, but if you continue scanning through page 1 and 2 of the search results, you’ll find one more tool called Overseer. I did not sample this tool for my research, but if for some reason Advanced Disk Space Monitor doesn’t float your boat, check this one out, and perhaps comment on it below. It has a long hyphenated domain name, which looks unprofessional to me, but I forgive them because finding the right domain to launch a software product is damn near impossible these days.
TL;DR
Most Windows disk space monitors suck. The one that doesn’t, Advanced Disk Space Monitor, will not be found on page 1 of a Google search of “Windows disk space monitor.”
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We’ve introduced a new enhancement to our popular auto follow-up feature which will send sequential follow-up emails in stages to people until they reply (or open, or click, or “reply or click“). Now you can set your auto follow-ups so that if you’re sending email to multiple people at a company or organization, if any one person at the organization replies, the follow-ups to everyone at that organization will stop. This option is useful if you’re cold emailing multiple people at an organization with the goal of getting just one of them to reply. If your goal is to get everyone at an organization to reply, you would not want to use this setting. This setting is OFF by default and needs to be turned ON if you wish.
This setting works by examining the domains of your recipients and stopping email to any domain that matches the domain of anyone that’s responded, with the exception of popular consumer domains.
For example, let’s say you’re cold emailing to pitch your corporate catering services, and your original email goes to 3 employees at Uber as well as 2 @yahoo.com addresses:
Because this setting works based on domain matching, if, for example, you had [email protected] on your list, [email protected] would continue receiving the auto follow-ups because uber.net is a different domain than uber.com. FYI, this is just an example, and it turns out that uber.net isn’t even owned by the real Uber.
When you activate this setting, it applies to your entire account, meaning it will apply to all campaigns with “no reply” auto follow-ups sent from your account. You can’t set this on a per-campaign basis. Also, it does not apply to auto follow-ups that are sent based on opens, clicks, or to ALL — it only applies to auto follow-ups that are based on replies.
To toggle this setting on and off:
Click Compose to launch a new window.
Set the To field to domainmatch@gmass.co.
Set the Subject to the word on or off.
Leave the Message blank.
Hit the GMass button. Do not hit the Send button.
Email marketing, cold email, and mail merge inside Gmail
Send incredible emails & automations and avoid the spam folder — all in one powerful but easy-to-learn tool
The GMass extension now works with both Gmail and Inbox.
How do you get it?
You don’t have to do anything to get GMass to work inside Inbox, if you already have the GMass Chrome extension installed in your browser. Just fire up Inbox and the GMass buttons should appear. If they do not appear, your Chrome browser may not have the latest GMass extension, version 4.0.0. If that’s the case, go to the URL chrome://extensions and click the button at the top to “Update extensions now”. Then confirm that your version of GMass is 4.0.0.
Newbie?
If you’re a Google Inbox newbie, these resources may help:
If your account is configured for it, go to Google Inbox now.
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In Gmail you have the ability to send not only from your @gmail.com or G Suite email address, but also any “alias” From Addresses that you configure in your Gmail Settings as well under “Send mail as”. If you then send a mail merge campaign “from” one of these alias addresses, it could impact your email deliverability because your emails may not get sent through Gmail’s high deliverability email servers.
How to add a new “From” address to your Gmail account.
It used to be that you could configure any additional address that you own to use as a From Address in your Gmail account and have those emails send through Gmail’s servers. A few years ago, Gmail changed that policy and now forces you to enter the SMTP server credentials for any new From Address you want to set up that isn’t hosted on Gmail or G Suite.
For example, I own the domain silicomm.com and one of my old email address is [email protected]. silicomm.com is NOT a G Suite domain. I actually run my own mail server for silicomm.com. My personal email account is [email protected], so if I want the ability to send “from” [email protected] inside my [email protected] account, then I’ll be forced to enter the SMTP server settings to send mail from [email protected].
When and why did Gmail make this change?
Gmail made this change around August of 2014. With the increase in usage of SPF and DKIM, it no longer made sense for Gmail to allow you to send emails from a domain that Gmail itself has no control over, through Gmail servers. Gmail was opening itself up to abuse by allowing people to send any emails they wanted from any domain they wanted through their email system.
On the other hand, you might be lucky and grandfathered in if you set up your Alias From Addressbefore Google made this change. I have the Gmail account, [email protected], and I set up [email protected] as an Alias From Address way back in 2012, so I was able to do so and still use Gmail’s servers. I haven’t touched the settings since…if I want to make any changes, I’ll be forced to enter an SMTP server.
Adding a new From Address to your G Suite account
If you run into a “permissions” error when trying to add a From Address to your G Suite account, you need to have your G Suite Admin make a change to your permissions to allow you to do so. By default, this permission is OFF.
In order to set up additional non-G Suite From Addresses in a G Suite account, your G Suite admin must set permissions to do so.
When does Gmail ask for the SMTP server?
Whether or not Gmail asks you to input an SMTP server when you add a new “Send mail as” From Address depends on the type of Gmail account you’re logged into and the type of From Address you are adding.
Gmail
G Suite
External Address
SMTP Server Required
SMTP Server Required
Gmail Address
No
SMTP Server Required
G Suite Address of Same Domain
N/A
No
G Suite Address of Different Domain
SMTP Server Required
SMTP Server Required
Regular Gmail
If you are logged into a regular Gmail account, meaning your account ends in @gmail.com or @googlemail.com:
Adding a non G Suite address, like [email protected] will force you to enter SMTP server credentials.
Adding a G Suite address, like [email protected] will force you to enter SMTP server credentials.
Adding another Gmail address, like [email protected] (Brian Smith is my alter ego), does not require you to input SMTP server credentials.
G Suite
If you are logged into a G Suite account, meaning your account ends in your organization’s domain and uses Gmail:
Similar to when you’re logged into a G Suite account, if you add a non G Suite address, like [email protected], you will be forced to enter SMTP server credentials.
If you add a G Suite address that belongs to the same G Suite domain as the account you’re logged into, you will NOT need to enter SMTP server credentials. For example, if I’m logged into [email protected], which is a G Suite account, and I add [email protected] as an alias From Address, I will not need to specify an SMTP server.
If you add a G Suite address that does NOT belong to the same G Suite domain, then you will be forced to enter SMTP server credentials. For example, if I’m logged into [email protected], which is a G Suite account, and I wish to add [email protected], which is another G Suite account, I will be forced to enter SMTP server credentials.
If you add a regular Gmail account as a “Send mail as” address, you’ll be asked to enter SMTP server credentials. Be careful here though — if you specify a third party SMTP server, you’ll likely fail SPF checks since you can’t control the SPF record for gmail.com to allow your third party SMTP server to send on behalf of gmail.com.
The skinny on deliverability
Let’s say that I now have [email protected] set up to send via [email protected]. The SMTP server for silicomm.com is mail.silicomm.com, and I enter this as the credentials.
I’m setting up a From Address of [email protected] and entering the SMTP server info for the silicomm.com domain.
If I now send a Gmail mail merge campaign from [email protected], those emails are routed through mail.silicomm.com and not Gmail’s high deliverability servers. My mail merge may work just fine, but I may lose some deliverability benefit. One of the advantages to using GMass over a traditional email marketing service like MailChimp or Constant Contact is the extremely high deliverability advantage that Gmail’s own servers provide over a traditional ESP’s servers, which are known to be bulk mailing servers.
The third party SMTP server may not be configured to handle rapid routing of many emails simultaneously. Some SMTP servers allow a single user to only send a couple hundred emails/day. In that case, you will be limited in the number of emails you can send not by Gmail’s own limits, but by the third party SMTP server’s limits. If you start to get bounces that are not generated by Google that indicate a rate-limit or delivery problem, then it’s the third party SMTP server is restricting you.
Here is an example of a bounce generated by a third party SMTP server: server173.web-hosting.com
An example of a bounce generated by a third party SMTP server, because of a quota issue.
A hack that allows you to still use smtp.gmail.com as your third party SMTP server
If you want to route your emails through Gmail’s servers even when sending “from” an external email address, you can use Gmail’s SMTP relay server, smtp.gmail.com. Whether you can use smtp.gmail.com and what credentials you use to authenticate into smtp.gmail.com depend on your setup.
G Suite
You can authenticate into smtp.gmail.com with any G Suite account just by using the G Suite email account and password as the credentials. You must turn on “Allow less secured apps” for this to work.
You must turn on “Allow less secure apps” for your G Suite account in order to authenticate into smtp.gmail.com with your G Suite email account and password.
If you don’t want to allow “less secure apps”, then you can turn on 2-step Verification and create a separate App password as described in the instructions below for Gmail. This will also work for a G Suite account.
Unlike with G Suite where the regular account email and password will authenticate into smtp.gmail.com if you turn on “allow less secure apps”, for regular Gmail accounts, you need to set up an app-specific password to authenticate into smtp.gmail.com. I consider this a loophole in Gmail’s policies, because I don’t believe this is what Google intended, but nevertheless it is possible to use smtp.gmail.com as the SMTP server for an external address inside a Gmail account. Someone else, far smarter than I, discovered this technique and wrote about it.
Example: Authenticating using a Gmail account from a G Suite account
Given that you can authenticate into smtp.gmail.com using a Gmail or a G Suite account, you can also now route your email in a complex manner via multiple accounts. For example, in my G Suite account [email protected], I can set up an Alias From Address of [email protected] (which is not a G Suite account) by authenticating into smtp.gmail.com with my regular Gmail account, [email protected]. Confused yet?
I’m authenticating into smtp.gmail.com with my [email protected] account. The password however is not the password for ajaygoel999, but a separate App password I created using this technique.
After Gmail tests the SMTP connection and sends me a verification code, I’m all set to send from [email protected] from my [email protected] account.
I’m now composing a mail merge using the [email protected] From Address.
Given that [email protected] is set to authenticate into the SMTP server with [email protected] account, which of my Gmail accounts will the email be sent from? [email protected] which is where I’ve set this up, or [email protected], which is the account the SMTP server will use?
The sent emails show up in the Sent Mail folder for [email protected].The emails ALSO show up in the Sent Mail folder for [email protected].
What account actually sent the 3 emails though? As expected, the [email protected] account actually sent the emails that are “From” [email protected], since it was the ajaygoel999 account that authenticated into the SMTP server. How do we know? A look at the headers of one of the received emails clues us in.
If you are sending via a third party SMTP server, must you adhere to G Suite’s/Gmail’s sending limits?
If you have configured a third party SMTP server (not smtp.gmail.com) to handle email for your new From Address, you might think you can now send as much email as you want. After all, why would Google care how much email you’re sending if it’s not going through their servers? It turns out that some sending restrictions are in place. I plan to do some further testing in our lab in the near future to determine just what the sending limits are when sending through a third party SMTP server. This will be the subject of a future blog post.
If you are using smtp-relay.gmail.com or smtp.gmail.com as your SMTP server, then the limits get even more confusing. Remember, the two SMTP relays aren’t meant to be used from inside Gmail. They are meant to be used by outside devices like printers and scanners and external email systems that need to relay email through your Gmail accounts.
Can you use a transactional email provider like Sendgrid or Mandrill as your SMTP server?
Yes. If you have an account at a transactional email service provider like Sendgrid, Mandrill, Mailgun, JangoSMTP, or any other email service provider, you can use the SMTP server credentials they provide you and enter it in the Gmail settings. Your emails sent “from” the new address will now be sent via the transactional email service provider instead of Gmail’s servers. You will likely suffer at least a tiny deliverability disadvantage though, since now your emails are being sent via an external service rather than Google’s own servers.
I have specified Sendgrid’s SMTP server to route my emails “from” [email protected]
SPF/DKIM considerations
If you’re sending via any third party SMTP server, ensure that the SPF record for you sending domain gives permissions to the third party SMTP server to send on behalf of your domain.
How the “Treat as an alias” setting matters for your mail merges
When you set up any new From Address, whether you check the Treat as an alias has no impact on how your email will look to your recipient. As the official Google document on “Treat as an alias” explains, the differences between checking this box or not only apply when you send an email to, or receive an email from, the new “Send as” address that you’re setting up. If you’re sending a Gmail mail merge campaign to 100 people, to them your email will look the same regardless of whether you have set the From to be treated as an alias or not.
Best practices
If you’re going to send mail merge campaigns from your Gmail or G Suite account, I recommend that you do it in the most direct way possible. Meaning, if you have a G Suite account for your own domain, and you want to send your emails “from” this email address, then log in to that account to send the mail merge, as opposed to using an @gmail.com account with the G Suite address set up as an Alias From Address.
If you want to send “from” an external address that is neither a Gmail nor a G Suite address, then you’ll be forced to specify an SMTP server. Unless you have an SMTP server configured to handle your mailings and deliver them, you should use smtp.gmail.com, because that guarantees high deliverability because it’s a Gmail server.
The bottom line
If you’re sending from a “From” address that is NOT a Google-hosted address, you will be asked to specify a third party SMTP server to relay emails through. You can use smtp.gmail.com as that third party SMTP server if you wish, or you can use an external SMTP server that you manage or one from a commercial service like Sendgrid or Mandrill.
Make sure that third party SMTP server can handle mass email campaigns, and make sure you configure the SPF record of your domain to grant permission to that server to send on behalf of your domain.
There are a lot of outdated articles on the web saying you can still send via Gmail, but many of them no longer apply.
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I’m launching an email newsletter today focusing on Gmail productivity!
If you’re a GMass user, then you’re also one of the 1 billion+ Gmail users on the planet. Every Thursday I’ll send you tips and tricks for maximizing your productivity inside Gmail. If you’re spending longer than you like managing email, then this is for you. The first issue is already out.
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Domain blacklists have been used to filter email for years, and in this comprehensive guide, I’ll cover:
The most popular public domain blacklists and lesser known, but equally important, private domain blacklists
How to determine if a domain is on a blacklist
How to get off each blacklist
Tips and tricks, gleaned from my own research and experience, about each blacklist
Given that GMass is an email marketing service used by over 200,000 people, we’ve seen our fair share of deliverability and spam issues. Because GMass works on top of Gmail and G Suite, we don’t maintain our own sending IP addresses. Instead, all email is sent from users’ Gmail accounts, meaning email originates from Gmail’s IP addresses.
Therefore GMass users almost never have to worry about an IP block. The one exception to this rule is if you’re sending from an alias From Address in Gmail and were required to input your own SMTP server credentials. In that case, Gmail routes your email through the external SMTP server, which makes the IP reputation of your SMTP server relevant. Far more common for GMass users, however, is the issue of domain-based blocking, since with the standard G Suite setup, your emails are sent from Gmail’s IP addresses.
Are domain blacklists the same as DNSBLs?
The term DNSBL is used often in the email deliverability industry. It stands for Domain Name Server Block List and refers only to the mechanism by which the block list is published (the Domain Name Server system). DNSBLs can be either lists of IP addresses or lists of domain names. Most DNSBLs are listings of IP addresses, and include popular blacklists like the Spamhaus Block List (SBL) and Spamcop. The blacklists that most concern GMass users are those that list domain names. This is because GMass sends emails from Gmail’s IPs, which are arguably the highest deliverability IP addresses in the world and aren’t blocked by anybody. Therefore it’s rare that an IP address will ever be the source of an email deliverability issue, except in the scenario mentioned above. A domain, however, can be the source of a deliverability issue.
This is a current and comprehensive guide to public and private domain-based email blacklists.
Overview
While IP-based email blocking is far more common, domain-based email blocking has gained popularity in recent years, and consumer email providers like Gmail and AOL and even corporate email filters like Barracuda, Symantec/MessageLabs, and Mimecast scan incoming email for the presence of domains on domain blacklists. If found, the email is rejected or sent to the Spam folder. This is why I’ve encouraged each GMass user to set up a dedicated tracking domain.
Domain-based DNSBLs fall into two categories: those that are publicly usable and searchable, meaning any email server administrator can use the list to filter email, and those that are private and used for an organization’s internal purposes only, like AOL’s. Plenty of email companies have written about domain blacklists previously, including Return Path and Sendgrid, but in this comprehensive guide, I’ll dig deeper into the nuances of both public and private blacklists.
Public Domain Blacklists
There are three main public domain blacklists: Spamhaus, SURBL, and URIBL.
Spamhaus DBL
Web lookup form:https://www.spamhaus.org/lookup/ Query via DNS: Query [domain].dbl.spamhaus.org and look for a response of 127.0.0.2 Tips and tricks: Spamhaus is the 300-pound gorilla of blacklists and publishes both an IP list and a domain list. Spamhaus will sometimes list domains that have never appeared in email flow before. It has an algorithm that detects newly registered domains, and if these domains meet a particular criteria, they are listed on the Spamhaus DBL without ever being included in a single email message. These domains are also the easiest to get delisted using the Blocklist Removal Form. Additionally, the email address that you enter to receive the confirmation removal link can determine whether your request is accepted and the link is sent, or your removal request is denied and you’re told to get in touch with Spamhaus staff. If your domain is ineligible for self-removal, you’ll have to contact Spamhaus and ask them to remove the domain, and that can be difficult.
You can attempt to remove a domain yourself from the Spamhaus DBL, but if a domain is ineligible for self removal, you’ll have to contact Spamhaus.
You’ll typically get a response within 24 hours. In my case with this domain, I didn’t get any explanation about the listing, even though it’s been used in very minimal email flow.
In this case, my Spamhaus delisting request has been denied.
SURBL
Web lookup form:http://www.surbl.org/surbl-analysis Query via DNS: Query [domain].multi.surbl.com and look for a response of 127.0.0.2 Tips and tricks: It’s relatively easy to get a domain off of SURBL, as long as you’re not a systemic spammer and have a reasonable explanation. In my experience, if you explain why your domain was used in spam and can show that you’re generally a responsible mailer, a few hours later, you’ll get a response accepting your request. I’ve never been turned down when asking for a domain to be delisted.
SURBL administrators are helpful in providing info and reasonable in delisting domains.
URIBL
Web lookup form:https://admin.uribl.com/ Query via DNS: Query [root domain].multi.uribl.com and look for a response of 127.0.0.2 Tips and tricks: The URIBL list is very difficult to get off. You can create a URIBL account and submit a delisting request, but in my experience, most delisting requests are denied. It also seems that whether a delisting request is accepted or not is at the whim of the person who is currently reviewing requests, given that only one out of all of my requests were accepted (for gmass.co), and the request was made just one day after the previous request was denied. Here’s my own history of delisting requests:
Most of my URIBL delisting requests were rejected.
Tips and tricks: The URIBL blacklist will be the subject of a future blog post, because it exhibits some rare and often quirky attributes. In our research though, it’s the least used of the three public blacklists. My own domain, wordzen.com, has been listed for a long time, and I’ve seen virtually no blocking of any email that includes the wordzen.com domain. Even MailChimp’s default tracking domain, list-manage.com, is grey-listed on URIBL.
Private Domain Blacklists
You might think that a private blacklist like the ones maintained by AOL, Barracuda, and Google are just that…private and un-searchable. While that may be true, it’s still possible to determine if your domain is on it. If you send an email with a listed domain to an address that uses a particular filter, the SMTP bounce response will indicate if the domain is on that private blacklist.
Barracuda’s Intent List
How to query: Use their web lookup form. DNS Lookup: There is no DNS-based method to look up a domain on Barracuda’s Intent List. Barracuda does provide a DNS method for querying their IP list, but not their domain list. It is possible, however, to examine SMTP responses to determine listings.
For example, if a domain is on Barracuda’s Intent List, you’ll get a bounce with an SMTP code from Barracuda that looks like:
Remote-MTA: dns; d124601a.ess.barracudanetworks.com. (64.235.154.140, the server for the domain d211.org.)
Diagnostic-Code: smtp; 550 permanent failure for one or more recipients ([email protected]:blocked)
Note that the specific domain that is on the list is not mentioned, so it will take some further analysis to determine the actual domain. How do we know that this response code is likely a domain-based block rather than an IP-based block? Because Barracuda’s response code for an IP-based block is specific to that IP address:
You might have noticed the difference between the two remote MTAs in these examples. In the first, the remote MTA is clearly a Barracuda-hosted server, because it ends with “barracudanetworks.com”. The second, dgcuda.com, appears to be an on-premise appliance running the Barracuda mail filtering software. Note the reference to “cuda”, which is likely short for Barracuda. Customers who install the Barracuda appliance can name the appliance whatever they like. Still though, the SMTP response codes will be equivalent regardless of whether the email server is hosted by Barracuda or hosted on-premise by an organization.
How to query: The only way to know you’re on AOL’s domain blacklist is if you receive an SMTP response code containing “HVU”, which stands for High Volume URL. Like Barracuda, the SMTP response won’t indicate which domain is blacklisted; it will only tell you that one or more domains present in the email are on the blacklist.
If a domain is on AOL’s private domain blacklist, the SMTP response from AOL will look like:
AOL denied my request to remove my domain from their domain blacklist.
Google’s Domain Blacklist
Google maintains a blacklist of domains, but the only way to tell if you’re on it, is to send an email to a Gmail or G Suite-hosted domain, and look at the reason you ended up in the Spam folder.
An example of Gmail-based domain blocking
SpamRL
How to query: The only way to know you’re on the spamrl.com’s blacklist is if you receive an SMTP response indicating that the URL is on the list.
This is what the bounce response from a spamrl.com block looks like
There is no web lookup form or DNS method to query the list.
SpamRL.com is a domain blacklist cloaked in secrecy.
When determining whether a domain is on one of the publicly searchable blacklists, I like to automate the process by programmatically doing the DNS lookup. As a secondary means, I’ll go to the website directly and use their lookup forms. An even easier way is to use a third party lookup tool that searches many blacklists at once.
Avoid Googling “DNSBL check”, and using one of the many forms in the search results that claim to check your domain or IP against a plethora of blacklists. This is because most lookup forms don’t properly perform the lookup against domain blacklists and instead do it against IP blacklists. An example is this lookup tool from MX Toolbox, https://mxtoolbox.com/blacklists.aspx. The prompt asks you to enter a domain or an IP address, but in reality, this check has nothing to do with domain-based blacklists. If you enter a domain, it simply converts your domain to an IP and then checks the IP against IP-based blacklists, which is entirely different from checking the domain-based blacklists that I’ve referenced above. Here’s another popular tool that does the same, converting your domain to an IP and only searching IP blacklists: https://www.ultratools.com/tools/spamDBLookup
An example of a lookup tool (that is buried deep in the search results) that does perform the correct kind of lookup is:
This intelligent tool, while prompting you for an IP or a domain, will determine WHETHER you entered an IP or a domain and tailor its search accordingly. If you enter a domain, the first set of results will be searching that domain properly against domain-based blacklists, however the domain blacklists it searches is limited to the publicly available blacklists that I’ve mentioned above. Here’s another tool that also performs the lookup correctly and also offers a proactive monitoring service:
Now that you have an overview of what the main public and private blacklists are, you are likely wondering which blacklists are relevant to your mailings. Does Gmail use these domain blacklists to filter their email? Does Outlook.com use them? Do corporate email filters like Barracuda, Mimecast, and Symantec/MessageLabs use them?
My research shows the following:
Spamhaus
SURBL
URIBL
AOL
Delivered
Delivered
Delivered
Gmail
Delivered
Uncertain
Delivered
Outlook.com
Delivered
Uncertain
Delivered
Yahoo
Delivered
Delivered
Delivered
Comcast
Uncertain
Uncertain
Uncertain
Barracuda
Delivered
Uncertain
Delivered
Mimecast
Blocked
Uncertain
Uncertain
Symantec/MessageLabs
Blocked
Delivered
Delivered
Testing methodology
I sent emails containing various blacklisted domains to a set of seed addresses
If the email containing the blacklisted domain made it to the Inbox, the blacklist/ISP combination receives a Delivered status. This is only indicative that the blacklist isn’t used to outright block email. It is not indicative that the blacklist doesn’t play a factor in determining overall spammyness.
If the email containing the blacklisted domain did NOT make it to the Inbox, in most cases, we designate that as Uncertain, since we can’t be sure if the fact that the domain was on the blacklist caused the block, or if the domain was already internally blocked.
In the cases where a blacklist/ISP combination is designated as Blocked, it’s because the blacklisted domain has such little email traffic that we can reasonably determine that its presence on a particular blacklist caused the block.
What you should do
You should regularly check the domains that are important to you and the domains that appear in your email flow against both public and private blacklists. For the public blacklists, there are several blacklist monitoring services that will periodically check your domains against Spamhaus, SURBL, and URIBL, and alert you of a listing. For the private blacklists, you should either manually scan your SMTP responses and look for patterns mentioned above, or you should programmatically check them (like we do for GMass users) to determine which domains are on private blacklists. GMass users needn’t worry about this, as this is handled by our internal deliverability monitoring tools. All GMass users’ domains are checked against the public blacklists once every hour and our intelligent private blacklist detection system works in near real-time.
Resources
The Wikipedia article on DNSBLs provides a good overview of how email blacklisting works. Be sure to read the part on URI DNSBLs though, because that’s the specific type of DNSBL that is a domain-based blacklist, as opposed to an IP-based blacklist.
Here’s a handy guide to the blacklists and lookup tools mentioned in this article:
Spamhaus DBL – Spamhaus’s domain block list lookup tool SURBL – The SURBL lookup tool URIBL – The URIBL lookup tool Barracuda – Barracuda’s Domain/IP lookup tool AOL – AOL’s contact form to request delisting of a domain SpamRL.com – their form to request delisting of a domain for 7 days
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There are certain situations where you may be eligible for a refund from GMass. For example:
You subscribed the wrong account, and now want a refund before you subscribe the correct account.
When you initially subscribed, you chose a plan that was incompatible with your account type (Gmail or G Suite), and you were auto-adjusted into the correct plan, but don’t want to pay the higher price.
You forgot you had an active subscription. You recently cancelled but haven’t used GMass in a while and would like the most recent charge refunded.
Not all accounts are eligible for a refund, and only the most recent charge is eligible for a refund. You must also have paid with a credit card via Stripe in order to use this automatic refund system.
To request a refund of your most recent charge:
Here I’m requesting a refund for the account [email protected]. If the refund is successful, the subscription for [email protected] will also be cancelled.
3. If you are logged into the Gmail account for which you seek a refund, leave the Subject blank. If you are logged into a different Gmail account, specify the account for which you are seeking a refund as the Subject.
4. Hit the GMass button. Do not hit the Send button.
You will be immediately notified if you are eligible for a refund and if your refund has been processed. If it is eligible for a refund, and it also has an active subscription, the subscription will be automatically cancelled at the same time the refund is issued.
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I just fixed a bug that was causing non-English characters in the To “Name” of a sent email to be corrupted. On the receiving end, the recipient, while receiving the rest of the email intact, would also see his/her Name in the To field corrupted.
The issue was due to the fact that GMass wasn’t properly using Encoded-Word format for the To header of sent emails. When you send a Gmail mail merge campaign in GMass, if you’re not using a spreadsheet containing your recipient addresses, you can place contacts directly in the To field of the Gmail Compose window. Gmail will add the Name of the contact if available. While the To Name portion of a contact can contain foreign characters, the email address portion cannot. For example, here is a campaign all set to go, containing foreign characters in the To Names, and these contacts are all Gmail Contacts, not from a spreadsheet:
This is a GMass campaign where the names associated with each email address contains foreign characters.
The MIME standard states that non-ASCII characters in the headers of emails must be properly encoded in Encoded-Word format, and while GMass was doing this for all other email headers, it was not for the To field. This is now fixed.
After the campaign is sent, the foreign characters in the Names of the “To” field are preserved, as seen in the Sent Mail folder, and as would also be seen by each recipient.
Note that this bug did not affect personalization in the Subject and Message. Meaning, if you had used {FirstName} or {LastName} in the Subject or Message, the personalization worked properly, even if the first and last names contained foreign characters. This was solely an issue with how the Name appeared in the To field.
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While 99% of GMass users experience the highest email deliverability they’ve ever experienced through any email marketing platform, sometimes users will ask us for help with a deliverability issue, because they believe that some of their email is landing in people’s Spam folders rather than Inboxes. GMass Campaign Reports do show blocks, which happens at the SMTP level, and is indicative of a content or domain-based blocking issue, but in cases where an email isn’t outright blocked and then generates a bounce, it’s helpful to know whether the email is making it to the actual Inbox or not.
Over time, I’ve built an array of tools to help our Support Team diagnose where a user’s emails are landing, the Inbox or Spam folder. When a user contacts us with a suspected deliverability issue, we first analyze the account and look at the open rates of the most recent campaigns. Some users have open rates of greater than 50%, and if we see that, we can usually conclude that there isn’t a widespread deliverability problem. If the open rate is lower, or we want to be thorough, then we conduct a seed list test. We have a simple way of taking any campaign in your GMass account and sending it from your Gmail account to several “seed list” addresses that we maintain. This list of about ten secret addresses are addresses across multiple email providers and email filtering systems, and they include at least one address in each of the following systems:
Gmail and G Suite (obviously)
GoDaddy Hosted Email
Outlook.com
Yahoo! Mail
Comcast
AOL
Barracuda
Symantec Email Security (formerly known as MessageLabs)
Mimecast
The first six (Gmail, GoDaddy, Outlook.com, Yahoo! Mail, Comcast, and AOL) are consumer email providers, and it’s easy to test Inbox placement at these domains, simply because anybody can sign up for a free email account at those providers, and then send their email campaign to these addresses to see if the email makes it to the Inbox. The next three (Barracuda, Symantec, and Mimecast), however, are the world’s three most popular corporate email filters, and surprisingly, most email marketers have never heard of them. I’ve secret-shopped all three such that I have at least one email address at each provider, so that I can test whether their filters are blocking or accepting a particular email message.
It’s also important to understand that the three corporate email filters don’t host email — they simply filter email and then pass the email to the email service that is the host, which for most corporations, is either G Suite or Microsoft Office 365. Therefore, it’s possible to host your company’s email on G Suite, but also, as an additional layer of protection, implement Mimecast or Barracuda or Symantec as the first line of defense.
How do you know if a domain has implemented such a setup? You need only look up the domain’s MX record. One of my domains is chromecompete.com, and I’m using Barracuda to filter its email. Here’s the MX lookup for chromecompete.com:
The MX lookup for chromecompete.com reveals that Barracuda is filtering its email.
So while you can discern that any @chromecompete.com address is using Barracuda to filter email, you cannot discern who the true email provider is…whether it’s G Suite, Microsoft Office 365, or something else. It turns out that I’m actually running my own Windows mail server (a platform called IceWarp) that hosts the email for @chromecompete.com.
As I mentioned, we have the ability to take a campaign from your account and send it, from your Gmail or G Suite account, to this list of addresses. Then we manually check each address to see whether the email arrived or didn’t arrive, and if it arrived, whether it landed in the Inbox, the Spam folder, or whether it was blocked by one of the corporate email filters. Additionally, our seed list tool allows us to easily vary elements of your email campaign, such as whether open and click tracking is on, what tracking domain is used, and the From Address. Even better, soon we’ll be making this tool available to you with the click of a button, and we’ll program our software to check if the email made it to the various email accounts and send a report back to you in a few minutes. Next, I’ll dig into some of the specific spam filters the seed-testing tool examines.
The Gmail Spam Filter
If your email campaign ends up in the Gmail Spam filter, Gmail accompanies it with an explanation that sheds some light on why it ended up there. Gmail has been doing this since 2012. We’ve generally seen five reasons when we see that a user’s emails are ending up in the Spam folder:
Generic content issue:
An example of an email in spam because of a content-related issue. This could be the result of a domain present in the body. Strange though, because this is a transactional email from Stripe, a well known payment processor, and coincidentally, the one GMass uses.
From Domain Issue:
An example of Gmail sending email to Spam because of the From Domain, which may be a G Suite hosted domain. If you’re a GMass user facing this issue, you should get in touch with G Suite support.
DKIM Domain Issue:
An example of Gmail sending email from its own paying G Suite customer to spam. If you’re facing this issue, we encourage you to contact G Suite support, because GMass staff doesn’t have the power to resolve this for you.
What’s shocking about this DKIM sample is it shows Google’s willingness to place email from its own paying G Suite customer in the Spam folder. As it’s explained on this page about how G Suite DKIM-signs emails, the gappssmtp.com domain is G Suite’s internal domain, meaning this email was sent by a G Suite customer and ended up in Spam folder.
Generic Issue:
An example of Gmail sending email to Spam based on heuristic data. Strange though, since Evite is a well known brand.
Phishing/Scam Issue:
An example of Gmail sending email to Spam for being a phishing email.
Given the variety of reasons Gmail may route an email to the Spam folder, even when it’s an email sent from a Gmail or G Suite account, this is how we would advise our users in each scenario:
From Domain or DKIM Domain Issue: Contact G Suite Support, since it’s your domain that’s been flagged, and it’s unrelated to anything GMass adds to your email.
Content-Related: We’ll use our seed testing tool to vary elements of your email to see if we can get it to the Inbox and what changes were necessary to make that happen.
Heuristic-Related: We’ll again use our tool to vary the content to see what works.
The Barracuda Filter
Inside the Barracuda control panel, I can highlight any message that’s been blocked by a Barracuda filter, and Barracuda will state why it’s been blocked, and even better, they’ll tell you if it was a particular domain that caused the block.
In this example, Barracuda blocks an email because of an SPF policy failure.In this example, Barracuda blocks an email because of the presence of a particular domain that is on its internal block list.
Based on the Barracuda reason, we’ll advise our user to take the appropriate action. In these examples, if it’s an SPF failure, we’ll advise our user to set up the appropriate SPF record, which is an easy fix. If the block is because of the Barracuda Real-Time System (BRTS) and a domain is specified, we’ll advise our user to eliminate that domain from the emails, and if the domain happens to be the tracking domain, we’ll have you swap out that tracking domain for another as an immediate workaround while we submit the blocked domain for delisting to Barracuda Support in the interim.
The Symantec/MessageLabs Filter
In this example, the Symantec/MessageLabs filter blocks a message based on the content.
In our experience with Symantec/MessageLabs, we’ve noticed little domain-based blocking, and when we have, it’s been tied to the domain being listed on a public blacklist, like SURBL or Spamhaus. We haven’t seen evidence of MessageLabs maintaining their own domain blacklist, so most blocks we see are content-based. So in cases of these blocks, we again vary the email with different tracking domains and tracking options to see if the email gets past the filter.
Google’s Postmaster Tools
In addition to use the seed-list testing tool, Google’s Postmaster Tools provides helpful data to determine what is happening to your emails sent to @gmail.com, @googlemail.com, and G Suite email addresses.
Set up Google Postmaster Tools for your sending domain and share the data with me at ajay[at]wordzen.com.We’ll take a close look at the Postmaster Tools in a future article, but you can set this up easily by adding your sending email domain to your account, and then sharing the data with us. Doing so will help us diagnose what is happening with your emails sent to Google-hosted addresses.
What if I’m on a blacklist?
There are two kinds of blacklists, IP-based and domain-based. It’s unlikely that your sending IP is blacklisted. In most cases, your emails are sent from Gmail’s own servers, so it’s almost impossible that your deliverability issue is caused by an IP issue, because only a foolish network administrator would ever block Gmail’s IP addresses. The exception to the rule is if you’re sending via an alias From Address you have set up inside your Gmail account. Gmail now requires you to specify an external SMTP server by which to send emails with an Alias From Address, so it is possible that the SMTP server you specify has an IP address that is on an IP blacklist.
If you’re experiencing lower open-rates than normal, then it’s possible one of the domains in your email is on a domain blacklist. Domain blacklists are either publicly searchable or private and internal to an organization. GMass encourages the use of dedicated tracking domains to isolate your domain reputation from that of other GMass users, since GMass isn’t a fully monitored system and it’s possible that a shared tracking domain ends up on a public or private domain blacklist. If your email isn’t outright blocked but instead ends ends up in Spam, it’s usually a content issue that involves either the actual text of the email, the From Domain, or the tracking domain present in the body. And if it’s the tracking domain causing the issue, we’ll pursue delisting of the tracking domain and replacement of the tracking domain during the time it takes for the delisting to happen.
In conclusion…
GMass employs a number of tactics to resolve the rare email deliverability issue that a user faces. We do the following:
Check your domain’s SPF records
Ensure your emails are DKIM-signed
Maintain seed addresses at every major email provider, both consumer and corporate
Additionally, you should share your Google Postmaster Tools data with us to give us an additional set of information to analyze. We are soon going to be releasing our automated “seed list testing” tool, so that you can conduct much of this analysis yourself, with the click of a button. Stay tuned!
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GMass runs on a farm of Windows servers, and as the chief systems administrator, one of the constant worries in the back of my mind is whether any of the disks on any of the servers is near capacity. Naturally, I decided to Google “Windows disk space monitor”.
