# Email Spam Tester

Last updated: 2026-09-17

> Send one email to a disposable address and get 41 technical checks back:
> SPF, DKIM, DMARC, TLS, reverse DNS, blocklists, HTML structure, link
> reputation and the bulk-sender rules Gmail and Yahoo publish. Every warning
> and failure carries the section of the RFC it rests on, quoted, and the page
> where the receiver states its own requirement. The first 100,000 reports
> are free for everyone: no key, no account, no signup. Built and run by Serhii
> Tanichev, an independent developer.

The loop is three calls and one email. Reserve an address, send the message you
were about to send your list to that address, read the report. The address
accepts exactly one message and expires in an hour; the report link is
permanent.

## For agents

- [Agent guide](https://email-spam-tester.com/skill/): when to reach for this,
  how to read the report, and which findings are DNS records a person has to
  change rather than text an agent can edit.
- [SKILL.md](https://email-spam-tester.com/skill/SKILL.md): the same as a file,
  served as plain text, ready to drop into a skills directory.
- [MCP server](https://email-spam-tester.com/mcp): streamable HTTP. Four tools —
  get_test_address, wait_for_report, get_report, get_message_source.
  wait_for_report blocks until the analysis is done, so there is nothing to poll.
- [MCP Registry](https://registry.modelcontextprotocol.io/v0/servers?search=io.github.serg-tanichev/email-spam-tester):
  listed as `io.github.serg-tanichev/email-spam-tester`, remote server only.
- [GitHub](https://github.com/serg-tanichev/email-spam-tester): the README,
  the changelog and ready-made MCP client configs.

## API

- [API reference](https://email-spam-tester.com/api-docs/): the loop, every
  endpoint, and what the fields in the report mean.
- [OpenAPI description](https://email-spam-tester.com/api/openapi.json)
- `POST /api/v1/inbox` reserves an address. Optional `lang` sets the language of
  the fix plan and the findings.
- `GET /api/v1/tests/{slug}/status` is the cheap thing to poll.
- `GET /api/v1/tests/{slug}` is the report. 202 until a message arrives.
- `GET /api/v1/tests/{slug}/message` is the message as delivered: headers in
  wire order, both bodies, the raw source.

## What the checks are

- [Every check explained](https://email-spam-tester.com/docs/): all 41, what
  each one measures, what it costs when it fails, and the standard behind it.

## Notes

- Two scores. `score_ours` is 0 to 100 and weights authentication and
  infrastructure heavily. `score_compat` is 0 to 10 and reproduces the
  SpamAssassin-style number for comparison with older tools.
- A check status of `skip` is not a pass: it means the check did not apply.
  `error` means it could not run and is excluded from the score.
- `complete: false` means something could not be checked. Treat the score as
  optimistic until it is true.
- Send the message from the platform that will send the campaign. Half the
  checks read headers the sending platform adds.
- A report shows the subject, the sender, the bounce address and the full
  source to anyone holding the link. Do not test somebody else's mail without
  asking.
- Available in 31 languages under a language prefix, for example
  `https://email-spam-tester.com/de/`. The API answers in English whatever the
  page language; `summary_localised` carries the translation when there is one.

## Who runs it

- [About](https://email-spam-tester.com/about/): Serhii Tanichev, independent
  software developer, whose day job is mail infrastructure for an email
  service provider. Email Spam Tester is his project, started in 2026.
- [Blog](https://email-spam-tester.com/blog/): notes on deliverability from
  real messages, by the developer. RSS at /blog/feed.xml.
  - [Why Are My Emails Going to Spam?](https://email-spam-tester.com/blog/why-are-my-emails-going-to-spam/): A developer who reads mail headers for a living walks through the real reasons a message ends up in spam, from SPF and DKIM alignment to your own reputation.
- [Changelog](https://email-spam-tester.com/changelog/): every change with its
  date.
- [Contact](https://email-spam-tester.com/contact/): hi@email-spam-tester.com.
- [Privacy](https://email-spam-tester.com/privacy/) and
  [Terms](https://email-spam-tester.com/terms/).

## Full version

- [llms-full.txt](https://email-spam-tester.com/llms-full.txt): the same ground
  with the whole loop, the report fields and the failure modes in one file.