SuperMailOS
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Send one email. See what receivers see.

Get a test address, send it an ordinary message from the mailbox you want to check, and get a score out of 10: authentication, the sending server, blocklists, content and links, each with its fix.

Opening soon

Test addresses aren't being handed out yet. Until they are, the email checker reviews your domain's setup in seconds, and the spam words checker scores your copy.

Email checker Spam words checker

01 What we check

Everything a receiver weighs, on one real message.

A domain can be set up perfectly and a message still land in spam. This test reads the message you actually sent, the way Gmail and Outlook do.

Authentication

Whether SPF passes for the server that sent it, whether the DKIM signature verifies against your published key, and whether DMARC lines up with your From address. We check each one ourselves rather than trusting what the message claims.

The sending server

Reverse DNS that points back to the same address, a proper greeting name, encryption on the way in, and whether the server's IP or your domain sits on a public blocklist.

The message itself

A plain-text version next to the HTML, a valid Message-ID and Date, one-click unsubscribe if it reads like bulk mail, and a Reply-To that stays on your domain.

Content and links

Wording filters associate with spam, images with too little text, links whose text names a different site, shorteners, insecure links and attachment types that get blocked.

02 Questions

Common questions.

Something else? Write to us — a real person answers, usually the same day.

Talk to us
How does the email deliverability test work?+
Get a test address, then send it an ordinary email from the mailbox or tool you want to check. When it arrives we check it the way a receiving mail server would and show a score out of 10, with every problem and its fix, biggest first. Each address takes up to five messages, so you can fix something and send again.
What should I send?+
The email you actually care about, written the way you'd really send it: a real subject and body, your usual signature, the newsletter you're about to ship. Content is part of the score, so a one-word test tells you less.
Does a 10 out of 10 mean my email will reach the inbox?+
No test can promise that. Gmail and Outlook also weigh your sending history and how recipients react, which no single message can show. A 10 means nothing in how this message was sent or written is working against you.
What happens to the email I send?+
It's analysed and discarded: never delivered anywhere, forwarded or replied to. We keep the report and the message headers for 7 days so you can share the link, then delete them. The body and attachments aren't stored.
My result hasn't appeared. What now?+
Mail can take a minute or two to arrive. Check the address was copied exactly, and look for a bounce in the mailbox you sent from: if your mail server couldn't deliver the message, the bounce says why.

03 More free tools

Keep checking.

Each tool answers one question about a domain's email. All free, no signup.

All free tools ▶
Authentication→

Email deliverability checker

SPF, DKIM, DMARC, MX and MTA-STS in one pass, with a score and the fix for anything that fails.

Reputation→

Blocklist checker

An IP, or a domain plus its mail servers, checked against public DNS blocklists.

Content→

Spam words checker

Highlights trigger phrases, shouting and risky links in your copy, with the reason for each.

Every check passing, on every domain you run.

Every domain you run in one inbox, from $3 a mailbox. 14 days free, no card.

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