MailSenpaiCheck your domainCheck
Free

Free tools for your email

Check and fix your domain’s DNS records, analyze emails that don’t arrive and bring the checks to your own website. Free, no sign-up.

  • Free
  • No sign-up
  • Plain English
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Check your domain

Email DNS checker

SPF, DKIM, DMARC and MX at once, with the report by email.

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SPF checker

A single record, its ending, DNS lookups under the limit of 10.

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DKIM checker

Key on the most common selectors or yours, length and revocation.

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DMARC checker

Policy, reports address, inherited record.

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MX lookup

Who receives the mail, priorities and spam filters.

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Create and analyze

SPF record generator

Choose the services you send from and copy the record.

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DMARC record generator

Policy, reports and options: the record to publish.

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Email header analyzer

SPF, DKIM and DMARC results and the server route.

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554 5.7.1 error

Why the email was rejected and how to fix it.

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For developers and agencies

DNS check widget

The check on your website with two lines of code.

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Free DNS check API

JSON, no key, CORS enabled.

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MCP server for AI assistants

The same check from Claude, ChatGPT and Cursor.

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Do your website or app emails still leave from the hosting server?

SMTP Senpai is the MailSenpai SMTP relay: it signs your emails with DKIM on your own domain, gives you the DNS records to publish and checks them for you. Servers and data in the EU.

Free · no sign-upCheck