There is a belief out there that any amount of mail merging will help spam proof your email — in other words, that mail merge deliverability is a given.

After all, you’re not sending a huge round of identical emails. You’re sending a huge round of mostly identical emails. And the word “mostly” is doing a whole lot of heavy lifting.

Unfortunately, running a Gmail mail merge is not some kind of foolproof deliverability shortcut. Blasting out hundreds of templated messages looks automated whether you’re personalizing using mail merge or not.

And some personalization techniques actually make things worse, as I’ll get into in this article.

But mail merge deliverability isn’t unsolvable.

There are techniques perfect for the unique challenges of sending personalized emails at scale — whether you’re onboarding new employees, inviting contacts to an event, following up with prospects, or any of the other infinite mail merge uses.

Here are the 10 most effective approaches I’ve found for getting mail merge campaigns into inboxes instead of spam folders.

Mail Merge Deliverability: Table of Contents

• 10 Proven Strategies to Improve Mail Merge Deliverability
  • 1. Master the email deliverability fundamentals
  • 2. Clean your merge data to avoid spam triggers
  • 3. Perfect your personalization balance
  • 4. Vary your templates without looking like a machine
  • 5. Handle merge field failures gracefully
  • 6. Segment your lists for better deliverability
  • 7. Manage volume vs. personalization strategically
  • 8. Track and manage mail merge-specific metrics
  • 9. Avoid the “mass personalization” red flags
  • 10. Test for spam on real mailboxes
• Mail Merge Deliverability Checklist
• How GMass Helps You Perfect Your Mail Merge Deliverability
• Ready to Improve Your Mail Merge Deliverability?

10 Proven Strategies to Improve Mail Merge Deliverability

Here are the techniques we’ve found for mail merge senders looking to make sure their messages hit the inbox.

1. Master the email deliverability fundamentals

Before we dive into the more nuanced, mail merge-specific strategies, you need to have the basics locked down.

These aren’t exciting, these aren’t a demonstration of cutting edge and innovative thinking — but they’re necessary:

• Set up SPF, DKIM, and DMARC authentication. These protocols prove you’re allowed to send from your domain.
• Set up a custom tracking domain. This makes sure your reputation isn’t affected by other senders.
• Clean your email list before every campaign. Bounces are always bad news, so knock out those damaging addresses early.

The good news is that tools like GMass handle most of the technical heavy lifting here.

• Here are beginner-friendly guides to set up SPF, set up DKIM, and set up DMARC. (You can also use GMass’s free email analyzer to check whether you already have those set up.)
• Here’s another easy walkthrough to set up a custom tracking domain.
• And GMass offers free email verification for your entire list with every plan.

These are the foundation on which you build everything else. Get them right, and the mail merge-specific strategies that follow will actually work.

2. Clean your merge data to avoid spam triggers

Ugly data in your Google Sheet of contacts leads to ugly merge outputs. Those scream “automation” to spam filters. Or, worse, to your recipients — who won’t hesitate to mark you as spam.

I’ve seen campaigns tank because someone had “JOHN DOE” in all caps, or company names like “MegaCorp | AI website builder.” that clearly came from scraping their website.

So clean up your data before you merge:

• Fix capitalization issues. “john smith” and “JOHN SMITH” both look automated — because you wouldn’t type someone’s name like that in a one-on-one message.
• Standardize company names. Remove weird suffixes, formatting inconsistencies, and anything you wouldn’t say colloquially. (For instance, if you were writing to someone at Microsoft, you’d say “Microsoft” and not “Microsoft Corp.”)
• Check for special characters. Apostrophes, accented letters, and other special characters may cause funky outputs.

Don’t forget: The goal with a mail merge is to make each email look like a human typed it individually. If your data looks scraped or auto-generated, your emails will too.

Need help? AI is actually pretty good at doing a lot of what I’ve described above. Check out this article I wrote on using an AI add-on to Google Sheets for data cleaning.

3. Perfect your personalization balance

Here’s the paradox: Too much personalization can actually hurt deliverability. Not instantly — but over time.

When you reference someone’s exact job title, company size, recent LinkedIn post, and hometown all in one email, it feels creepy and obviously automated. That can increase people marking you as spam which, in turn, vastly increases your likelihood of going to spam.

Stick to personalization that feels natural:

• Use first names reliably. But understand that no one is “fooled” into thinking they’re getting a one-on-one email anymore by you using their first name alone.
• Reference relevant details sparingly. One or two personalized touches are good, not ten.
• Avoid “stalker-level” personalization. Mentioning their kid’s soccer team or saying you just looked at their Puerto Vallarta vacation photos is too much.
• Make it contextually relevant. Don’t personalize just because you can. For instance, throwing out someone’s college name with no context just shows you know how to scrape. (Mentioning their college because you also went there is a different story.)

The best mail merge campaigns feel like individual emails that happen to be sent at scale. The worst ones feel like robots trying too hard to sound human — or humans who used AI as a shortcut to actually doing some research.

4. Vary your templates without looking like a machine

Even with merge fields, email providers can and will detect template patterns.

When 500 emails have the exact same structure with only a few words swapped out, you’re not going to fool a modern, AI-driven, high-powered spam filter.

Smart template variation goes beyond basic merge fields:

• Use conditional content. Try different opening lines based on company size or industry.
• Rotate subject line variations. Use three or four different versions that convey the same message.
• Use spintax. Spintax varies up your email with slight rephrasing.
• Change call-to-action placement. Sometimes at the end, sometimes mid-email.

Once again, the good news is that mail merge tools like GMass can handle all this.

• Here’s a guide to using conditional content to add some simple if…then options to your messages.
• Here’s how to rotate your subject lines with GMass’s inline A/B testing.
• Here’s how to use spintax — and better yet, how to use GMass’s SpinMax, which spins every email in your campaign in one click.

5. Handle merge field failures gracefully

Nothing screams “mass automation” like an email that says “Hi ,” because you didn’t have a contact’s first name in your Google Sheet.

And it happens more often than you’d think.

You need to set up your merge logic defensively:

• Always use fallback values. “Hi there” instead of “Hi ,” when names are missing.
• Test your merge syntax. Preview actual merged emails before sending.
• Handle edge cases. What happens with names like “Mary-Kate” or “O’Connor”?
• Check for data formatting. Phone numbers and dates can break if formatted wrong.

This handful of steps alone will save you a ton of mail merge issues.

• Here’s how to use fallback values to deal with missing contact data.
• Here’s how to create drafts of your mail merge messages so you can preview (or at least spot check) them before sending.

6. Segment your lists for better deliverability

Sending to your entire 2,000-person Google Sheet at once can be a deliverability killer.

Email providers notice when you suddenly blast thousands of emails in a short timeframe, even if they’re personalized. (Especially if you usually send around three to 10 emails a day, then suddenly you jump into the thousands.)

Mail merge naturally lends itself to segmentation.

We know you have data about your recipients — you’re using it in the merge. So it’s easy to filter your list or divide it into chunks around commonalities in your recipients.

Smart segmentation improves your inbox rates:

• Break large lists into smaller batches. Try to get down to segments of around 200 or so recipients.
• Segment by engagement history. Plan how you’re going to send to your most engaged contacts. (First? Last? Mixing them in randomly?)
• Use geographic or demographic splits. It’s smart to split your list based on different time zones, industries, or roles. Time zones can be best because then you can send during targeted work hours.
• Space segments appropriately. Wait a few hours or days between batches. Or send different batches from different mailboxes.

This approach also lets you test and optimize. If your first segment performs poorly, you can adjust the template before sending to the remaining segments.

How do you pull this off? Once again, there are tools that can do so much of this for you.

• Here’s how you can filter which rows of a Google Sheet are used in a campaign.
• Here’s how you can vary up the sending order of your Google Sheet. (Alphabetically? In order? Randomize?)
• Here’s how to schedule your sends, so you can set start and end times for a segment.
• And here’s even a technique for using different sending accounts.

7. Manage volume vs. personalization strategically

The more emails you send at once, the more automated you look — regardless of personalization. But, on the flip side, spreading your sends too thin can hurt your campaign momentum and response rates.

Find the sweet spot:

• Respect daily sending limits. Don’t max out your account’s capacity in one campaign.
• Use throttling wisely. Add pauses between messages to spread sends over hours, not minutes.
• Consider your normal email patterns. Sudden volume spikes look suspicious.
• Match your sending to your business. A real estate agent sending 1,000 emails daily looks different than a consultant sending 50. Context really does matter, especially as email clients get smarter.

GMass will automatically break up your campaign across multiple days if you hit your account’s sending limit — but you can also specify a daily sending cap as well to keep things tighter.

And here’s how you can use throttling to add those pauses between your messages.

8. Track and manage mail merge-specific metrics

Mail merge campaigns have different engagement patterns than broadcast emails, and you need to track them differently.

Monitor these mail merge-specific metrics:

• Bounce rates by data source. Which Google Sheets, lists, and especially prospecting tools are causing problems?
• Engagement by personalization level. Do highly personalized emails actually perform better?
• Template variation performance. Which subject lines and content versions work best?
• Segmentation results. How do different batches compare?

Pay special attention to unsubscribe patterns. If people are opting out at higher rates from your mail merge campaigns than your regular emails, your personalization might be coming across as creepy rather than helpful.

You can always check your real-time analytics for any campaign (or, if you need to do some serious data crunching, download your campaign results as a CSV or Google Sheet).

9. Avoid the “mass personalization” red flags

The biggest mail merge deliverability killer is looking obviously automated despite the personalization.

Certain patterns immediately give away that you’re sending at scale.

Red flags to avoid:

• Identical send timestamps. 500 emails sent from a single account in an abbreviated time frame looks automated.
• Perfect template consistency. Every email having the exact same structure.
• Unnatural personalization patterns. Everyone gets personalized in the exact same spots.
• Bulk-style subject lines. Even with names, “Hi {FirstName}, Quick Question” screams mass email.

The goal is making each email feel individually crafted, even though you’re using automation to send hundreds. It’s about being smart with your automation, not obvious about it.

10. Test for spam on real mailboxes

So… once you’ve done everything I’ve covered above, it’s time to find out if you’re in the clear.

Spam Solver is a tool that sends a test version of your mail merge campaign to ~20 real inboxes and lets you know your ratio of inbox to spam placement.

And if you’re still hitting spam folders, it will give you suggestions to improve your campaign — then you can re-test to see if your inbox rate is higher.

You should run every campaign through Spam Solver before you send. That way you’ll avoid surprises and you’ll know definitively whether or not you’re destined for spam.

Mail Merge Deliverability Checklist

Before you hit send on your next mail merge campaign, run through this quick checklist:

Technical Setup:

• [ ] SPF, DKIM, and DMARC authentication configured
• [ ] Custom tracking domain set up
• [ ] Email list cleaned and verified
• [ ] Sending volume appropriate for your account’s reputation

Data and Content:

• [ ] Merge data cleaned (proper capitalization, formatting, no special characters)
• [ ] Fallback values set for missing merge fields
• [ ] Template variations created (subject lines, content, CTAs)
• [ ] Personalization level feels natural, not creepy

Campaign Strategy:

• [ ] Large lists segmented into smaller batches
• [ ] Sending schedule spreads volume appropriately
• [ ] Test emails sent with actual merge data
• [ ] Tracking set up for mail merge-specific metrics

Final Testing:

• [ ] Merged emails previewed across different data scenarios
• [ ] All links and personalized elements working correctly
• [ ] Campaign doesn’t scream “mass automation”
• [ ] Spam Solver test checks out

How GMass Helps You Perfect Your Mail Merge Deliverability

GMass was originally built as a way to get Gmail mail merge campaigns into inboxes — and it’s still doing that for hundreds of thousands of senders today.

Here’s how GMass solves the unique deliverability challenges we’ve covered:

Built-in deliverability tools

Spam Solver is GMass’s secret weapon for mail merge deliverability. It tests your actual merged emails (not just templates) across real inboxes at major providers, then gives you AI-powered recommendations for improving your inbox rates. You’re not guessing whether your campaign will work — you’re testing it with real data.

Email verification happens automatically before your campaign goes out. Bad email addresses get flagged and excluded, protecting your sender reputation from bounces that could tank future campaigns.

Custom tracking domains let you control your own reputation instead of sharing it with thousands of other senders. Your links go through your domain, not a shared tracking service that might already be flagged.

SpinMax creates natural content variations automatically. Instead of sending 500 identical emails with just names swapped, you can send 500 genuinely different emails that still convey your core message.

Smart sending features

GMass makes it easy to send mail merge campaigns that don’t look like mass automation:

Advanced scheduling lets you distribute large campaigns across hours or days automatically

Throttling controls help you manage sending speed to match your normal email patterns

Holiday and weekend skipping prevents your campaigns from going out on the wrong days when people don’t want to be bothered.

Professional support

When you’re dealing with mail merge deliverability issues, generic email support doesn’t cut it. GMass provides:

Deliverability guidance from experts who understand mail merge challenges.

Technical support for complex merge scenarios and edge cases.

Best practice recommendations based on data from hundreds of thousands of campaigns.

Ready to Improve Your Mail Merge Deliverability?

Mail merge deliverability isn’t about tricking spam filters — it’s about sending real personalized emails that provide value to recipients.

Whether you’re onboarding new employees, updating donors, following up with prospects, or anything else, the strategies we’ve covered in this article will help ensure your important messages actually reach their intended audience.

GMass makes it easier to get mail merge deliverability right from the start.

The platform handles the technical complexity while giving you easy-to-use tools to create campaigns that feel genuinely personal at scale and that reach the inbox.

Ready to check it out yourself — and to see why nearly 400,000 users rely on GMass (and give it an average rating of 4.8 out of 5 stars)?

Install the GMass Chrome extension and try it free — no credit card required. You’ll be sending your mail merge campaign in a matter of minutes.