@ed_meyer
Thanks!

@jamison
The Exim configuration is the main configuration on the server for many email options. You do not have access to this unless you have root access to your server.

The default address should not be enabled per your post, the contrary. it should be disabled.

This is the main address for each Unix user and to make things simple when describing it for this case, it is one of the main problems for users where emails arrive that have the same "From" and "To" address.

Disabling it in your cPanel > Mail > Default Address is a very good idea for most users.