Mail merge errors are a particularly acute genre of email embarrassment.

There’s nothing quite like being the person who sent “Dear {first_name” to 500 potential clients.

Or, even worse, the person who accidentally sent Bob’s confidential salary information to Alice.

The good news?

Mail merge mistakes are, by and large, 100% avoidable.

They usually happen because of:

• Small oversights in your spreadsheet
• Data or URL formatting issues
• Not properly testing your merges before you send
• Or, overall, just rushing

In this article, I’m going to walk you through the most common mail merge errors I see all the time — and, more important, how to prevent them from happening in the first place.

Some of these fixes are simple (like cleaning up your column headers).

Others require a bit more savvy. And if you’re using Gmail’s built-in mail merge tool… well, let’s just say there are some errors you literally can’t prevent.

But never fear. By the end of this article, you’ll know exactly what to look for, how to troubleshoot when things go sideways, your best option for Gmail mail merge tools, and how to set yourself up for mail merge success every single time.

Mail Merge Errors: Table of Contents

• The 8 Most Common Mail Merge Errors in Gmail
• How GMass Helps You Avoid Mail Merge Errors

The 8 Most Common Mail Merge Errors in Gmail

Here are the most common mail merge mistakes and issues I help people with on a daily basis.

1. Merge Fields Not Populating

This is the prototypical mail merge fail.

You think you’re sending “Hi Sarah,” but Sarah gets “Hi {FirstName,” and now she thinks you don’t know how to use basic technology. You’re also pretty much guaranteed not to get a response.

Common causes:

• Extra spaces in your column headers (“First Name” vs “FirstName”)
• Different capitalization (“firstname” vs “FirstName”)
• Special characters or symbols in headers
• Changing the name of a column in your Google Sheet before you send
• Mistyping syntax (like “{{FirstName}} or {FirstName instead of {FirstName}”)
• You hit the blue Send button in Gmail, not your mail merge software’s send button

How to fix it:

As you can see, most of your problems are going to come from issues in your Google Sheet column headers. (That’s the first row of your Google Sheet; every Google Sheets mail merge tool uses those column headers as your merge tags.)

Keep your headers simple and consistent. Use things like “FirstName,” “Company,” or”EmailAddress” with no spaces and no weird characters.

And make sure the merge fields in your email template match those headers exactly.

(In an app like GMass, there’s no concern here — typing a left curly brace will bring up your list of column headers so you don’t have to type them out by hand.)

And I’m going to say this a whole lot in this article: Before you send anything, run a test with your own email address and info to see how the merge fields populate.

2. Empty Fields Creating Awkward Gaps in Emails

For example: “Hi Sarah, I saw that   was recently featured in TechCrunch and wanted to reach out.”

Or, of course, the classic: “Hi ,”.

Common cause:

• You don’t have a piece of data in your Google Sheet for a contact. In the first example, you didn’t have Sarah’s company name filled in. In the second example, you didn’t have the recipient’s first name.

How to fix it:

There are three solutions when you don’t have every single piece of data for every single contact.

The first are fallback values. That’s where you add a default; for example “Hi {FirstName|there},” — so that way, you’ll get “Hi there,” if you don’t have a person’s first name.

The second solution is conditional content. That’s a little more complicated, but it allows you to use if…then logic. This is good in situations where a single fallback value might not be one size fits all.

And finally, another solution with GMass is auto first-name detection. GMass will aim to determine the first name from the person’s email address and include it if it finds it.

3. Formatting Issues (Bold/Italics Not Working, Line Breaks Missing)

You carefully format your email template with bold headers and perfect spacing.

Then your recipients get a wall of text that looks like it was typed by someone who’s never seen an email before.

Common cause:

• Copying and pasting content from other sources (like Word docs or websites) that brings hidden formatting with it.

How to fix it:

Make sure you’re using a mail merge tool that lets you create emails directly inside the Gmail compose window. That’s your best bet to make sure all formatting looks right throughout the process.

If you just have to copy your email content, paste it into a plain text editor first, then copy it again into your email template. (Or, if you can pull it off, you can even send a plain text email.)

4. Wrong Data Appearing for Recipients

This is the nightmare scenario.

You’re sending a mail merge with personalized attachments, sending out tax forms — and Bob gets Alice’s salary information.

That’s not the only disaster that can happen. Maybe your competitor gets a proposal meant for your biggest client. Or maybe you’re doing outreach for jobs and you send a message to someone at Uber telling them how excited you are at the chance of working for Lyft.

Common cause:

• Your spreadsheet rows get misaligned.

How to fix it:

This one isn’t on your mail merge software — it’s on you.

Always double-check your spreadsheet alignment. Make sure each row corresponds to one person and that there are no empty rows or columns throwing things off.

Also, it wouldn’t hurt to make sure every contact is only in your Google Sheet one time so you aren’t sending duplicate emails to people (and possibly with slightly different info).

And with any mail merges that are super mission critical, you can take things a step beyond sending yourself a test.

Use the Just Create Drafts feature to create drafts of every single message in your campaign. Then you can spot check them to make sure everything looks right across the board.

5. Images Not Displaying Correctly

Your beautiful company logo shows up as a broken image icon.

Your product screenshots are nowhere to be found.

Or those personalized images you created for every prospect all come up as broken picture icons.

Common cause:

• You pasted in an image and now it’s trying to link to a file that isn’t publicly accessible or a broken URL.
• You’re mail merging in personalized images but have the URLs wrong.

How to fix it:

This is another reason why it’s best to compose your emails in the Gmail compose window.

There, you can embed images rather than linking to them on an external server. Google prefers that; it might even give you a little deliverability boost.

Now, if you’re sending personalized images to your recipients, the error is probably different. Both Google Drive and Dropbox really obscure and hide the actual URLs of your image files.

Follow our personalized images and attachments guide to drill down to the real file links. They don’t make it easy on you — but if you can actually get to these links, your mail merged images will work.

6. Emails Going to Spam

Your email campaign lands in spam. Could it be your mail merge fields?

Common cause:

• Almost certainly not anything to do with your mail merge content.

How to fix it:

I included this in my list because people ask me all the time about mail merge and spam issues… but really, your mail merge fields are rarely going to be the cause of deliverability problems.

If anything, mail merge should help you because you’re not sending out a ton of identical emails — and, in theory, mail merge messages get better engagement because they’re more targeted and actionable.

If you’re worried about deliverability issues with your mail merge, the best thing you can do is: Actually find out if you’re going to have problems.

Run your campaigns through Spam Solver before you send them. That will tell you if you’re headed for the inbox or spam folder by testing on actual mailboxes.

And if the verdict is spam, then it will give you suggestions to fix that before you send your campaign.

7. Attachments Not Sending or Wrong Attachments

You say you’re attaching a proposal… but your personalized proposal PDF (that’s a hell of a tongue twister) isn’t actually attached.

Common causes:

• Incorrect file names or paths.
• To a lesser extent, file permission or size issues.

How to fix it:

As I noted in the section on image issues, in virtually all the cases I’ve seen with mail merge attachment issues, the problem is caused by Google Drive and Dropbox’s obtuse link structure.

So if you’re going to send personalized attachments, make sure your files have the right permissions, they aren’t too large — and then, make sure you really drill down to their actual URLs.

And this is another case where it really makes sense to create your campaign as drafts to spot check before sending.

8. Campaign Stopping Mid-Send

Your 500-person campaign stops after 243 messages sent and you have no idea why.

Common causes:

• You hit Gmail’s daily sending limits.
• Recipients are on your unsubscribe or bounce list, so messages to them are being suppressed.

How to fix it:

Know your sending limits. Free Gmail accounts can send up to 500 recipients per day; paid Google Workspace accounts can send up to 2,000.

If your campaign is larger than that, make sure you know how your mail merge tool will handle it.

Gmail’s built-in tool has a hard limit of 1,500 recipients per campaign. Other apps do as well.

Some, though, have real solutions. With GMass, the software will automatically pause your campaign if it detects you’ve hit your daily limit and will resume sending the following day. (Or, you can use one of GMass’s techniques to break Gmail’s limits and send virtually unlimited emails in a single day.)

The other possible issue here is people are on your unsubscribe or bounce lists, so your messages aren’t going out to them. This can also happen if you’re working with a team and you’re sharing unsubscribe lists — people could be unsubscribed from your organization without you even realizing it.

How GMass Helps You Avoid Mail Merge Errors

As you’ve (hopefully!) seen from this list, mail merge errors are pretty avoidable with:

1. Knowing the root cause of issues.
2. Taking the time to properly test campaigns before sending.

Tools like Google Workspace’s built-in mail merge and YAMM are… fine for very basic campaigns. But they’re missing a lot of the features that would help you catch errors before they happen.

GMass, on the other hand, was built specifically to handle the complexities of mail merge campaigns without the headaches.

Draft Creation Feature

With GMass, you can create drafts of your campaign to see exactly how each email will look before you hit send. No more guessing whether your merge fields will populate correctly — you can literally preview Bob’s email and Sarah’s email to make sure everything looks right.

All looks good? Click a link to send.

Something’s off? Click a different link to delete the drafts, then head back to the compose window to fix things.

Test an Entire Sequence

With GMass, you can use mail merge in every follow-up message to your campaign.

And you can test the entire sequence by sending it to yourself with a single click — to make sure the merges are working at every stage.

Better Merge Field Management

GMass handles merge fields more intelligently than Gmail’s native tool and the others. You can use fallback values, conditional content, and even personalized images, links, and attachments without worrying about technical hiccups.

Deliverability Tools

Remember that spam folder issue? GMass has Spam Solver, which tests your campaign against real inboxes and gives you AI-powered suggestions to improve your deliverability before you send. No more hoping your emails make it to the inbox.

(GMass also has lots of other great deliverability tools as well, including email address verification, custom tracking domains, and more.)

Unlimited Sending Capacity

GMass can break through Gmail’s daily sending limits, so your campaigns won’t stop mid-send. You can either distribute large campaigns across multiple days automatically or use SMTP servers to send virtually unlimited emails in a single day.

Professional Support

When something does go wrong (because, let’s be honest, if you send enough campaigns something will probably trip you up), GMass has an actual support team who can help you figure out what happened and fix it. Gmail’s mail merge tool has one help doc and that’s it.

The bottom line: mail merge errors are mostly avoidable with the right preparation and tools.

Gmail’s native mail merge is good for personal sending, but if you’re sending campaigns that actually matter for your business, you probably want something more robust.

GMass is free to try — no credit card required — so you can test out all these error-prevention features on your own campaigns. Just install the Chrome extension and you’ll be up and running in minutes.