How to run a domain reputation check in Mailtester and what to do with the results

If you send emails for a living—sales, newsletters, customer updates—you've probably worried about whether your messages actually land in inboxes or get sent straight to spam. You’re not alone. Most people don’t realize that “domain reputation” can quietly tank their deliverability, even if their lists are squeaky clean.

If you’ve heard about Mail-tester (here’s Mail-tester), you might be wondering if it’s any good for checking your domain’s reputation—and more importantly, what you should actually do with the results. This guide is for anyone who wants real answers, not vague advice.

Let’s dig in.


What Is Domain Reputation, Really?

Before you run any checks, let’s get clear on what domain reputation means. In plain terms: it’s how email services (think Gmail, Outlook, Yahoo) rate your sending domain. If your domain has a bad reputation, your emails are more likely to get marked as spam or blocked.

What affects your reputation? - Spam complaints - Sending to dead or fake email addresses - Bad technical setup (missing SPF, DKIM, DMARC) - Sending lots of emails in a short time

You can do everything else right, but if your domain reputation is trashed, your deliverability will suffer.


Step 1: Prepare Before You Check

Don’t just jump in and run a test. Here’s how to get a result that actually reflects your real sending situation:

1. Use your real sending setup.
Send from your actual email tool (Mailchimp, Outlook, CRM, etc.), not just your Gmail account. The point is to test what your recipients experience.

2. Check from the domain you use for bulk or business email.
If you send from sales@yourcompany.com, test that domain.

3. Send a typical message.
Don’t send a blank email or one that looks nothing like your usual campaigns. Use a real template or message.

Pro tip:
If you use multiple sender addresses or tools, run separate tests for each. Results can vary.


Step 2: Run a Domain Reputation Check in Mail-tester

Here’s the honest truth: Mail-tester doesn’t give you a full “domain reputation” score the way some paid tools (like Google Postmaster Tools) do. But it does give you a realistic snapshot of how your emails look to spam filters, including some insights about your domain.

How to use Mail-tester:

  1. Go to Mail-tester.
    You’ll see a unique email address (like test-abc123@mail-tester.com) on the page.

  2. Send your real email to that address.
    Use your actual sending tool and settings, not just a manual forward.

  3. Wait a few seconds, then click “Check your score.”
    Mail-tester will fetch your email and run its tests.

  4. Review your score (out of 10) and the detailed breakdown.
    The report covers spamminess, technical issues, and blacklists.

Quick reality check:
Mail-tester is best for checking if you’re making obvious technical mistakes and if your emails look “spammy.” It doesn’t have a magic window into Gmail’s secret algorithms.


Step 3: Make Sense of the Results

You’ll get a score, usually between 0 and 10. Here’s how to read the report without getting lost:

1. SpamAssassin Score

  • This is a spam filter used by many mail servers. A high score here means you look suspicious.
  • What to do:
    Mail-tester usually explains what triggered the score. Fix anything major (like “HTML_IMAGE_ONLY_24” means your email is just a big image, which is a red flag).

2. Blacklist Checks

  • Mail-tester checks if your domain or sending IP is on public blacklists.
  • What to do:
    If you’re blacklisted, that’s serious. Check the specific blacklist site. Sometimes, it’s a false alarm. If you’re genuinely on a list, you’ll need to clean up your act (more on that below) and request removal.

3. SPF, DKIM, DMARC

  • These are technical settings that “prove” you are who you say you are.
  • What to do:
    If you see a warning or fail, fix these asap. Your IT person or email provider should know how. There are lots of guides online, but if you use Google Workspace or Microsoft 365, they have step-by-step help.

4. Content Analysis

  • Mail-tester looks for “spammy” words, too many links, or weird formatting.
  • What to do:
    Don’t panic over a single “trigger word.” Focus on obvious problems: all-caps, too many exclamation marks, or emails that look like a phishing attempt.

5. Broken Links and Images

  • Broken images or links can hurt your score and look unprofessional.
  • What to do:
    Fix any broken stuff. It’s basic, but it matters.

Step 4: What Actually Matters (and What Doesn’t)

Mail-tester gives you a lot of info. Here’s what’s worth your time:

Worth your attention: - Fails on SPF, DKIM, or DMARC - Being on a real blacklist (not just minor ones) - High SpamAssassin score with clear reasons - Broken links or images

Ignore or don’t stress over: - Warnings about “missing unsubscribe links” if you’re just sending a test
(But yes, real campaigns should have them.) - Minor points off for a single “spammy” word
- Reports about “no text version” if your tool only sends HTML (most do)

Common gotchas: - If you’re sending from a new domain, your reputation will be neutral or unknown—don’t expect miracles. - If you use a shared sending service (like Mailchimp), your domain reputation is partly tied to their infrastructure.


Step 5: How to Fix (or Improve) Your Domain Reputation

If Mail-tester shows real problems, here’s what to do:

1. Clean up your technical setup. - Set up SPF, DKIM, and DMARC. There are online wizards and guides—don’t skip these. - Make sure your “From” address is consistent and matches your domain.

2. Fix content issues. - Ditch spammy words and over-the-top formatting. - Use real text, not just images. - Add a plain-text version if possible.

3. Stop sending to bad addresses. - Remove bounces and unengaged users from your list. - Never buy lists. Ever.

4. Deal with blacklists. - If you’re blacklisted, go to the blacklist site and look for their removal process. - If you’re not sure why, review your sending history—maybe someone reported you, or you sent to a spam trap.

5. Warm up new domains. - Start with small batches, not blasts. - Build up slowly over weeks.

6. Use feedback loops and monitor complaints. - Some services let you know when users report you as spam. Pay attention and adjust.

Pro tip:
Don’t obsess over getting a perfect 10/10 on Mail-tester. Focus on fixing real issues. Chasing tiny points can waste hours with zero real-world benefit.


Step 6: What Mail-tester Can’t Tell You

Mail-tester is a great “canary in the coal mine,” but it’s not all-seeing. Here’s what it won’t tell you:

  • How Gmail, Outlook, or Yahoo will actually treat your email.
    They use proprietary algorithms and reputation data you can’t see.

  • Your true sender reputation across all inbox providers.
    For that, you’d need access to things like Google Postmaster Tools (and even that’s limited).

  • How your email performs over time.
    One test is a snapshot. Things can change fast.

Bottom line:
Mail-tester will catch the obvious stuff. If you fix those, you’re ahead of 90% of senders.


Step 7: Keep It Simple, Monitor, and Iterate

Don’t overcomplicate things. Here’s a sane way to use Mail-tester:

  • Check before major campaigns or after making changes.
  • Fix the big problems (technical and content).
  • Ignore the noise.
  • Watch your real-world open rates and deliverability. If they tank, dig deeper.

Remember, perfect scores aren’t the goal—inbox placement is. Focus on sending useful, wanted emails with a clean setup, and you’ll be just fine. And when in doubt, run another test and keep learning.