Too many "Received" headers - suspected mail loop

Symptoms

When sending an email, the email is bounced with the following failure:

Too many "Received" headers - suspected mail loop

Description

This is typically caused by a smarthost being configured, and the problematic domain not having its mail routing set to local. You can verify a domain's mail routing by running the following command:

grep ^DOMAIN.TLD /etc/{remote,local}domains

Please note, you will want to replace "DOMAIN.TLD" with the problematic domain you want to verify the mail routing of.

Workaround

Set the problematic domain's mail routing to local. You can view details on how to change the mail routing for a domain here:

How to change the MX or Mail Routing for a domain in WHM