Everything a mail server checks, explained.
SpamBarometer runs your real email through the same kinds of checks receiving servers use, then tells you in plain English what to fix first.
Authentication: SPF, DKIM and DMARC
Authentication is how mailbox providers know an email really came from your domain. Without it, good email is filtered or rejected.
We check your actual headers against your domain’s DNS records, including the alignment problems most checkers miss, such as DKIM signing as your email provider’s domain instead of yours.
Authentication-Results: mx.spambarometer.com; spf=pass smtp.mailfrom=bounce.mailer-esp.net; dkim=pass header.d=mailer-esp.net; dmarc=fail (p=quarantine) header.from=yourshop.co.uk
SpamAssassin, rule by rule
SpamAssassin is the open-source filter behind spam scoring at many mail providers. Instead of one number, you see every rule your email triggered, how many points it added, and what it means.
Rules are ranked by impact, so you fix the one adding 2.5 points before the one adding 0.1.
| Rule | What it means | Points |
|---|---|---|
| HTML_IMAGE_ONLY_24 | Almost no text, mostly images | +1.3 |
| SUBJ_ALL_CAPS | Subject written in capitals | +0.5 |
| MIME_HTML_ONLY | No plain-text version | +0.1 |
| DKIM_VALID | DKIM signature checks out | −0.1 |
Content, links and design
We measure the balance of text to HTML, images without alt text, whether there’s a plain-text version, and whether the email works on mobile.
Every link is listed by domain, with URL shorteners and suspicious patterns flagged. We also check which CSS properties break in Outlook, Gmail and other clients.
Sending reputation
Your sending IP and domain are checked against the major blocklists, including Spamhaus, SpamCop and Barracuda.
If a list refuses our lookup, we say so plainly instead of guessing, so you never chase a listing that isn’t there.
| Spamhaus | Not listed | |
| SpamCop | Not listed | |
| Barracuda | Not listed | |
| URIBL | Couldn’t check |
AI rewrites Premium
Rule-based checks tell you what’s wrong. AI suggestions go further, with rewrites for your subject line and body copy, ordered by how much each should help.
Suggestions sit alongside the measured checks, never instead of them.
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Sentence case and a single clear offer. This removes two triggered rules.
With a free account
5 tests a day instead of 2, plus somewhere to keep them.
Test history
Every report saved, with your scores over time on your dashboard.
PDF reports
Download any report as a PDF to share with your team or a client.
API access
Run tests from your own systems. Ask us about access.