How to fix 550 Please turn on SMTP Authentication email error in cPanel

After using transfer tool to transfer a single cPanel account from one server to another, transfer tool failed to detect the email routing settings for some of the domains, and the weirdest thing happened: no routing setting was set for the domain names.

As a consequence, all emails sent to these domains is rejected with the following error message:

Message not delivered

550 Please turn on SMTP Authentication in your mail client. mail-yw1-f48.google.com [209.85.161.48]:32858 is not permitted to relay through this server without authentication.”

To fix this, simply head over to cPanel > Email Routing and recheck the “Auto Detect” or “Local”

Select the domain name and re-set the desired option:

After doing that the emails should start receiving normally.