Mail errors · Microsoft 365 and Outlook

What does “5.7.23 The message was rejected because of Sender Policy Framework violation” mean?

The receiving server checked your SPF record and the sending server failed it.

Last read from the sources at the foot of this page.

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Microsoft Outlook
5.7.23

The message was rejected because of Sender Policy Framework violation

As Microsoft prints it.
01

What does it mean?

The receiving system uses SPF to decide what to accept, and your record did not list the server that sent this message, or could not be read.

02

What exactly does the source say?

5.7.23 The message was rejected because of Sender Policy Framework violation The destination email system uses SPF to validate inbound mail, and an issue affects your SPF configuration.

03

Why would a small firm see it?

A missing service in the record, two SPF records, or more than 10 lookups.

04

How do I fix it?

  1. List every service that sends mail as your domain: your mailboxes, your invoicing or accounting tool, your booking system, your newsletter tool, your website's contact form.
  2. Find each service's SPF include in its own help pages.
  3. Send yourself a message through the service and open its headers.Look for spf=pass.

Keep one SPF record. Add the service inside the one record you have, before its last word, and keep every service already in it. A second SPF record makes the check fail for every message.

An SPF record may make at most 10 DNS lookups. Each include counts, and so do the includes inside it. Past 10 the check fails, so take out services you no longer use before adding a new one.

Sources

Where does this come from?

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