Free Email Spam Tester

Why this is worth ten minutes

A newsletter that lands in Promotions still counts as delivered. Your sending platform reports 99% delivery and shows you nothing else. The distance between "delivered" and "read" is where campaigns quietly die, and nothing on your side of the send is looking at it.

Most of what decides that distance is technical, and none of it is visible from where you are standing: a DNS record with a syntax error, a header the receiving server expected and did not find, an IP address somebody else burned last month (a neighbour on shared hosting, or whoever had it before you).

What happens to the message you send

You get a disposable address. Send it the message you were about to send your list: the real one, with the real links and the real sending setup behind it.

It arrives at a mail server that behaves the way a receiving one does. The server verifies your signatures, reads your DNS, asks two independent spam engines what they make of the content, and looks your sending address up in more than twenty blocklists. Nothing to install, and the address works once and expires in an hour.

Reading the report

Two scores. One reproduces what the classic SpamAssassin-based testers give this exact message, so the number is comparable to what you have seen elsewhere. The other is ours, and it covers ground the classic method never looked at: the bulk sender rules Gmail and Yahoo began enforcing in 2024, link reputation, one-click unsubscribe.

Under that, 42 checks with the evidence behind each one. Every warning and every failure carries the section of the RFC it comes from, quoted, and the page where Google states its own requirement. You can check us.

Then a plan for this message: what to change, in what order, and how many points each change is worth (the points are recomputed by scoring the fixed version, not estimated).

What a spam score actually measures

A spam score is a running total of penalties. Every filter rule your message trips adds points, and the classic SpamAssassin threshold is 5. Below it the message passes, at or above it the message is spam. So the scale runs the wrong way round from the one most people expect. A low score is the good one, and the 10 out of 10 that testers show you is a count of the points you did not lose.

The rules doing the counting are unglamorous. An image with no text around it, a subject line in capitals, a From domain whose DNS does not authorise the server the message came from, a link shortener somebody else burned last year. Each rule is worth a fraction of a point, and the points are what accumulate. A message rarely fails on one rule (that would be easy to find), it fails on eleven of them adding up quietly while you were looking at the design, and no single one of those eleven looks like the culprit when you go back to check.

We give two scores for the same message. One reproduces the classic SpamAssassin number, so it is comparable to whatever other spam score checkers have told you. The other is ours, and it counts what the classic number never looked at, which is the bulk sender rules Gmail and Yahoo began enforcing in 2024, link reputation, one-click unsubscribe.

How to test email deliverability

Send the message you were about to send anyway. Not a two-line draft written for the test. The real one, with the real links and the real platform behind it.

Then check three layers separately, because they fail separately. Authentication is DNS, and SPF, DKIM and DMARC either line up with the server the message came from or they do not. Reputation is your domain and your IP as the receiving side has been recording them, blocklists included. Content is what the filters make of the words, the links, and how much of one there is against the other.

One test is one snapshot. That snapshot describes one send and nothing further, so run the test again after each change. The fix plan recomputes the points by scoring the corrected version instead of estimating what the correction ought to be worth, which means you can see whether anything moved.

The full walkthrough, step by step →

Sender score is a different number

Sender score usually means something narrower. It is a reputation rating for one sending IP address, published by Validity on a 0 to 100 scale, and there a high number is the good one. It describes the address you send from across weeks of history, so complaint rates go into it, spam trap hits go into it, and so does volume that jumped on a Tuesday when nothing else about your sending had changed.

A spam score describes one message. The score and the sender score are independent, and they fail independently. Immaculate content from a burned IP lands in spam, and a spotless IP will not rescue a message that trips eleven content rules. Fixing the wrong one is the ordinary way a week disappears.

This tester answers for the message and for the setup behind it. If your reputation is what is wrong, the report says so and names the blocklist, and that is the part you can act on today.