SMTP code:550 msg:550 5.7.1 Email rejected per DMARC policy for strapi.io

Questions and Answers Strapi Backend
1
System Information
  • Strapi Version: 4.25.11
  • Operating System: Ubuntu Linux
  • Database: MySQL
  • Node Version: 19.9.0

Hello,

I am facing the following error when attempting to register a new user with email confirmation enabled:

SMTP code: 550 msg: 550 5.7.1 Email rejected per DMARC policy for strapi.io

This error doesn’t seem to make sense for two reasons:

  1. The email sending configuration in plugins.ts is correctly set up and does not use the strapi.io domain.
  2. Test messages can be sent successfully via /admin/settings/email, and they are received without any issues.

What could be causing this problem?