I dove in, learned that she was using Canned Responses, a Labs feature of Gmail, and decided to use it myself. What I discovered was shocking: Canned Responses interacts with Gmail’s internal architecture in such a way that it breaks the functionality of many Gmail extensions, including GMass.

Without Canned Responses:

When you launch a Gmail Compose window, and start typing, you might notice that every few seconds, the URL in the address bar of the browser changes. That’s because Gmail is saving your message every few seconds and internally, generating a new “Message ID”, an internal identifier for your message. You can try it yourself. Launch a Compose window, and type a few characters in the Subject field, and you’ll notice that almost immediately the URL changes to include this Message ID.

With Canned Responses:

Now do a test where you launch a Compose window, and don’t type anything in any of the fields. Instead, choose to insert a template from your Canned Responses menu. The Subject and Body will populate, but notice how a “Message ID” is never generated. Gmail hasn’t yet saved the message. Many Gmail extensions, including GMass, rely upon Gmail saving the message and generating a Message ID in order to “tag” the message to perform some function. Now just type a character or word, anywhere in the Subject or Message fields. Voila! You should now see a Message ID in the URL.

Another side effect of using a Canned Response with GMass is that when clicking the GMass button to send your campaign, you may get a popup alert telling you that your Subject line is blank, even though your Subject line isn’t blank. Keep reading to learn how to work around this issue.

So the trick is…

The trick to using Canned Responses successfully with GMass or any other Gmail extension is to make at least one more change to your message after inserting the Canned Response. That can include something as simple as typing a character in the Subject or Message and then just deleting it. That will be enough to trick Gmail into saving the message and generating a Message ID that includes your Canned Response.

With GMass specifically, you can ensure your Canned Response is appropriately set by using the Send Test Email function by clicking the Settings arrow next to the main GMass button. If the test email arrives as you expect, then you know you can send your mail merge campaign.