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Email & DNS

Microsoft 365 Email DNS Checklist

Build a Microsoft 365 email DNS checklist using tenant values you provide.

Calculations run in your browser. The tool does not send your inputs to a server.

01Your inputs

Local workspace

Start with the sample below, or enter your own values.

Copy this tenant-specific target from Microsoft 365 admin centre. Do not derive it from the domain name.
Optional. Copy the exact selector CNAME target shown for this custom domain in Microsoft 365.
Optional. Copy the exact selector CNAME target shown for this custom domain in Microsoft 365.
Optional. Use a monitored mailbox or reporting service that is ready to receive DMARC aggregate XML reports.

02Your result

Your result will appear here. Choose an action after checking your inputs.

A quick guide

How to use this tool

  1. Check the example and the unit beside each input.
  2. Enter your values and choose Build.
  3. Review the result and assumptions, then copy what you need.

Reset example restores the starting values. Clear removes text and number inputs, returns choices to their first valid option, and removes the result.

Reference guide

Explanation and worked examples

The MX and DKIM targets are tenant-specific and must be copied from Microsoft 365 admin centre. Keep one SPF record, then enable DKIM and monitor DMARC before enforcement.

Use in day-to-day IT work

Prepare a mail or DNS change, or interpret evidence from a delivery investigation.

Checks before applying the result

  • Record existing DNS values and TTLs, identify the authoritative provider, and prepare rollback values.
  • After publishing, query authoritative DNS and check actual message headers or delivery reports. These tools do not query live services.
New to the terminology?
SPF
Sender Policy Framework: authorises sending hosts for a domain used by SMTP.
MTA-STS
A published policy for authenticated TLS delivery to declared MX hosts.
TTL
How long a DNS answer may normally remain cached.

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