A free mail-tester alternative: test your email’s spam score

Why look for a mail-tester alternative

mail-tester.com is a good tool and has been the reference for years. It runs your message through an out-of-the-box SpamAssassin install, checks SPF, DKIM, Sender-ID and DMARC, looks up your IP on common blocklists, tests your links and images, and reverses SpamAssassin’s score so that 10/10 is the goal.

People usually go looking for an alternative for one of three reasons:

• The free allowance. mail-tester allows three free tests per 24 hours. When you are fixing DNS records one at a time, three runs go quickly.
• A 10/10 that is too easy. A message can pass SPF, DKIM and DMARC and look clean to a stock spam filter while its domain still publishes a monitoring-only DMARC policy, a 1024-bit DKIM key and no MTA-STS. Those are exactly the details that separate a working setup from a robust one.
• The 2024 sender rules. Google and Yahoo now require one-click unsubscribe for bulk marketing mail and valid reverse DNS for every sender. A test that scores those explicitly saves you reading the requirements yourself.

How check.adbtd.com works

1. Open check.adbtd.com and start a test. You get a one-off address like test-AB12CD34@check.adbtd.com, valid for 24 hours.
2. Send a real email to it from the mailbox you want to test: your normal client, your sequencer, your application. Use the actual campaign copy, not “test”, because content is scored too.
3. The result page fills in within seconds of the message arriving: a score out of 10, pass / warn / fail for every check, and for each problem, what was observed and how to fix it. Share the link with whoever manages your DNS, or append ?format=json to get the result as JSON.

No account, no email address to hand over, and no tracking of the message body: the raw message expires after 24 hours and the body is never rendered on the result page.

What it tests

Around 40 checks in seven groups, plus a full scan by Rspamd, the open-source spam filter many mail servers use.

How the score works

The score starts at 10. Each check that fails or warns removes a fixed number of points: a DMARC failure on the message itself costs 4, an invalid DKIM signature 3, a Spamhaus listing 3, a missing PTR record 1.5, a DMARC policy of p=none 1.5, a missing TLS-RPT record 0.4. Spam symbols from the Rspamd scan that no explicit check already covers are deducted at their own weight.

The rule is simple: 10/10 means perfect, every check passed. Between 8 and 10 the message is inbox-ready with room to improve; between 5 and 8 it is likely to land in Promotions or be filtered; below 5 it is likely to be rejected or sent to spam.

That makes check.adbtd.com stricter than the bulk-sender rules themselves. Google accepts p=none as a valid DMARC policy; we still take points off for it because a policy that enforces nothing does not protect your domain. If you only want to know whether you meet the minimum, read the authentication tiles at the top of the result rather than the headline number.

check.adbtd.com vs mail-tester.com

mail-tester.com details from its FAQ, pricing and API documentation, as of October 2026.

When mail-tester is the better choice

• You want the score everyone already quotes. “10/10 on mail-tester” is a shorthand clients and colleagues recognise.
• You need results kept longer than a day, or a paid volume plan, API or embeddable tester for an agency workflow.
• You want broken-link checks; check.adbtd.com does not fetch your links.

When check.adbtd.com is the better choice

• You are iterating on DNS and need more than three runs a day for free.
• You want the details behind a robust setup scored: DMARC enforcement, DKIM key size, SPF lookup budget, MTA-STS, TLS-RPT, one-click unsubscribe.
• You want each blocklist shown separately with a link to its lookup tool, and a JSON result without a paid plan.

The five most common failures and how to fix them

• DMARC p=none. Fine for the first weeks while you read aggregate reports. Once every legitimate source passes, move to p=quarantine, then p=reject.
• SPF over ten lookups. Every include: costs lookups, and over ten the whole record returns a permanent error. Remove services you no longer send from, or replace includes with explicit ip4: ranges.
• 1024-bit DKIM key. Rotate to a 2048-bit key with a new selector, publish it, then switch signing over.
• Missing or generic PTR. The reverse DNS of your sending IP should resolve to a hostname that resolves back to the same IP. On shared platforms you cannot change it; on a dedicated IP you should be able to.
• No one-click unsubscribe. Add List-Unsubscribe and List-Unsubscribe-Post: List-Unsubscribe=One-Click headers. Google and Yahoo require them for bulk marketing mail.

For the full picture of what Google, Yahoo and Microsoft now require, see our cold email infrastructure setup guide.

For adbtd customers: scoring through the API

The same scorer is available as POST /api/v1/check on the adbtd API, which takes a raw RFC 5322 message and returns the breakdown as JSON, so you can score templates in CI before they ever go out. Every outbound message sent through an adbtd mailbox is also scored automatically, and the dashboard shows the trend. See the API reference.

Frequently asked