Mail-Tester Explained: How to Read Your Spam Score

Mail-tester.com scores a single email from 0 to 10 by running it through SpamAssassin, checking your SPF, DKIM, and blacklist status, and grading your content and links. A 10/10 means the message is clean and correctly authenticated, not that it will land in the inbox. This guide walks through every section of the report, what a good score actually is, and the gap between passing mail-tester and passing Gmail.

Most explanations of mail-tester stop at "send an email, get a number." That number comes from a specific, well-documented engine with specific rule categories, and reading the report section by section tells you far more than the headline score does. This article breaks down how the score is built, what each part of the report means, and what mail-tester structurally cannot see, so you stop chasing a perfect 10 and start fixing the thing that actually keeps your mail out of spam.

Key takeaways

• Mail-tester runs your email through a default SpamAssassin install, then inverts the raw penalty score into a 0 to 10 scale where higher is better. A raw SpamAssassin score near 0 shows as close to 10.
• The report has five parts: overall score, SpamAssassin content and header rules, authentication (SPF, DKIM, rDNS), blacklist status, and a check for broken links or spammy structure.
• 8/10 or higher is a reasonable bar for a first pass. Chasing 10/10 past that point has diminishing returns; a lower score with a clear authentication failure matters far more than a high score with a minor content flag.
• The free tier gives you 3 tests per rolling 24 hours and a random test address each time, which is enough for occasional checks but not for monitoring every send.
• A perfect score does not guarantee inbox placement. Mail-tester grades configuration and content, not sender reputation, domain age, or how a specific mailbox provider's proprietary filter treats you.

What mail-tester actually checks

You go to mail-tester.com, copy the unique, randomly generated test address it shows you, and send your real email to it from your actual sending tool, not a stripped-down test message. Click "Then check your score" and it analyzes the message it just received.

Under the hood, mail-tester runs a default, out-of-the-box installation of SpamAssassin, the open-source spam filter mail servers have used for over two decades. SpamAssassin normally produces a raw penalty score where more spam signals mean a higher, worse number, and a message typically gets flagged as spam around a raw score of 5. Mail-tester inverts that scale for readability: a clean message with almost no flagged rules shows as close to 10/10, and one with several rule hits drops toward 0.

On top of the raw SpamAssassin pass, mail-tester layers its own checks: your domain and IP against a set of DNS blacklists, your SPF and DKIM records against the domain you sent from, your reverse DNS (rDNS), and a scan of your HTML and links for structural problems like broken URLs or an unusually high image-to-text ratio.

The five sections of a mail-tester report

Reading the score in isolation is the most common mistake. The report is organized into distinct sections, and each one answers a different question.

1. The overall score

The headline number out of 10. It is a sum: start near 10, and each flagged rule below subtracts a fraction of a point depending on how severe that rule is. A missing DKIM signature costs more than one overused word in your subject line.

2. Content and header analysis (SpamAssassin rules)

This is the SpamAssassin engine itself, checking your subject line, body copy, and headers against thousands of pattern-matching rules: spam-trigger phrases, excessive capitalization, HTML formatting problems (hidden text, mismatched font colors, inline style abuse), a missing plain-text version of an HTML email, and structural header issues like a mismatched From name and address. Each triggered rule appears in the report with a short label so you can see exactly what tripped it, not just that something did.

3. Authentication (SPF, DKIM, rDNS)

Mail-tester checks whether your message passes SPF (is the sending server authorized for this domain) and DKIM (is the message signed and unaltered), plus whether your sending IP has a matching reverse DNS entry. These are pass/fail checks against DNS records you control, and a failure here is usually the single highest-value fix in the report, since SPF and DKIM failures are also what trip the DMARC checks mailbox providers increasingly enforce. If you have not set these up yet, our SPF, DKIM, and DMARC guide walks through the exact records to publish.

4. Blacklists

Mail-tester checks your sending IP and domain against a set of DNS-based blacklists (DNSBLs). A listing here can tank deliverability even when your content and authentication are flawless, because many mail servers reject or junk mail from a listed IP before they ever read the content. If you are listed, our email blacklist check guide covers how to find out which list flagged you and how to request delisting.

5. Links and technical structure

A scan for broken links, insecure (non-HTTPS) links, and a check on your unsubscribe setup and general HTML cleanliness. Small individually, but they compound: a message with three broken links and a heavy image-to-text ratio reads as low-effort or automated to a content filter, even with perfect authentication.

What a good mail-tester score actually is

Mail-tester's own guidance is to aim for a perfect 10/10, a fine target for a template headed to your full list. In practice, most senders treat 8/10 or higher as a solid pass for day-to-day sending and save the effort of chasing the last point or two for high-stakes sends.

The score is not linear in importance. A 9/10 that lost a point to a slightly aggressive subject line is a very different problem than a 6/10 that failed DKIM. Read the per-rule breakdown before you react to the headline number: fix any authentication failure first, then blacklist listings, then content and structural flags. Chasing the number without reading what caused it is how people spend an afternoon rewriting copy when the real issue was a missing DKIM CNAME record.

Free tier limits and how to run the test correctly

Mail-tester's free tier gives you 3 tests per rolling 24-hour window, and each test uses a newly generated, one-time address. That is enough to sanity-check a template before a broadcast, but not enough for continuous monitoring across many campaigns, which is what paid plans and dedicated deliverability platforms are for.

To get a result that means something, send the actual email you plan to broadcast: real subject line, real content, real links, from the real sending tool and domain you will use for the campaign. A stripped-down test message will score better than your production email and tell you nothing useful. Copy the generated address fresh each time, and read the full report, not just the top number, before you decide anything passed or failed.

Mail-tester versus other deliverability tools

Mail-tester answers one specific question well: is this message configured and written cleanly. It does not answer where your mail actually lands across real inboxes, or how your domain is trending in reputation over time. Here is how it compares to the tools that answer those questions.

None of these, including mail-tester, can tell you whether a specific real human opened your email. That is a gap only your actual sending platform can close, by sending the real campaign to real test recipients and reporting a genuine open, not just a passed spam check. For the fuller picture of how these checks fit together before a send, see our complete email deliverability guide.

Why a perfect score still lands in spam sometimes

This is the most consistently reported gap across mail-tester users, and mail-tester says as much in its own FAQ: a perfect score does not guarantee delivery, because every mailbox provider runs its own proprietary filtering on top of the generic checks a tool like SpamAssassin performs.

A few things sit entirely outside what mail-tester measures:

• Domain and IP age. A brand-new sending domain gets extra scrutiny from major providers regardless of how clean the message is. Mail-tester has no way to see how old your domain or IP is.
• Sender reputation and engagement history. How past recipients on that specific provider have opened, replied to, deleted, or marked your mail as spam shapes filtering far more over time than any single message's content. Our sender reputation guide covers how that reputation is built and protected.
• Per-provider proprietary models. Gmail, Outlook, and Yahoo each run additional filtering mail-tester cannot replicate, which is why a message can score 10/10 and still land in one provider's spam folder while landing clean everywhere else.
• List quality. Sending a clean, well-authenticated message to a stale or purchased list still generates complaints and bounces that a one-off content score cannot see.

Treat a high mail-tester score as confirmation that your configuration is not the problem, not as proof that delivery is solved. It rules things out; it does not rule the inbox in.

How to fix common mail-tester failures

• SPF fails or is missing. Publish or correct your SPF TXT record so it authorizes every service that sends on your domain's behalf, including your marketing platform and any transactional sender.
• DKIM fails. Confirm your provider's DKIM CNAME or TXT records are published in DNS and that the signing selector matches what your sending service actually uses.
• Listed on a blacklist. Identify the specific list, resolve the underlying cause (often a compromised sender or a stale list with high complaint rates), then submit that list's own delisting request.
• Content or structure flags. Add real text alongside images, remove flagged trigger phrases, fix broken links, and make sure your unsubscribe link is present and functional.
• High score, still in spam. This points to reputation, engagement, or domain age, not configuration. Warm the sending domain gradually and prioritize your most engaged contacts first rather than editing the message further.

Where Meisa fits

Mail-tester is a useful, free pre-send check on a message's configuration. What it cannot do is tell you what happened after you hit send. Meisa is an email platform for SaaS teams that runs on your own Amazon SES, so the sending reputation you are protecting is yours, not shared with other tenants on someone else's platform. It verifies your domain with SPF, DKIM, and DMARC, and its open-rate analytics distinguish genuine human opens from Apple MPP and corporate-scanner opens, which is the closest thing to real feedback you get once a message leaves the test stage and reaches your actual list.

If your immediate need is a one-off spam-score check before a single send, mail-tester's free tier does that job well on its own. See our email deliverability guide for how testing, authentication, and ongoing monitoring fit together, or visit meisa.io to see how sending and true open-rate analytics work once you move past the test stage.

FAQ

What is a good mail-tester score?

8/10 or higher is a solid score for regular sending. 10/10 is achievable and worth chasing for a template you will reuse across many sends, but the specific rule that cost you a point matters more than the number itself. A 9/10 lost to a minor content flag is a non-issue; a 6/10 lost to a failed DKIM check is urgent.

How many free tests does mail-tester give you?

The free tier allows 3 tests within a rolling 24-hour period, using a newly generated test address each time. That covers occasional pre-send checks but is not built for testing every campaign variant or monitoring deliverability continuously.

Why did I get 10/10 on mail-tester but still land in spam?

Mail-tester grades your message's configuration and content, not your sender reputation, domain age, or a specific provider's proprietary filtering model. A perfect score confirms your authentication and content are clean; it says nothing about how Gmail or Outlook has learned to treat your specific sending domain over time.

Does mail-tester check SPF and DKIM?

Yes. It validates SPF (whether your sending server is authorized for your domain) and DKIM (whether the message is signed and unaltered) directly against your DNS records, plus your reverse DNS setup. A failure in either is usually the highest-priority fix in the whole report.

What is the difference between mail-tester and an inbox placement test?

Mail-tester scores one message against a generic spam filter and a set of blacklists. An inbox placement tool like GlockApps sends your message to a seed list of real inboxes across providers and reports whether it actually landed in the inbox, spam, or a specific tab. Mail-tester tells you if the message is clean; a placement test tells you where it actually went.