Email authentication - username vs. username@domain


Apr 30, 2019
Denver, CO
cPanel Access Level
Root Administrator

I am in the process of migrating an old mailserver over to an account on cPanel. On the old mailserver, users had their own system (Linux) accounts, and therefore could authenticate with just the username, no domain - and most do authenticate that way - just username.

On cPanel, where this mail is being migrated to, I have created a parent account for all of these users, I then have created email accounts under the account for these users, e.g. [email protected].

When trying to setup an Outlook profile, it does not accept just the username when authenticating, but instead I am required to input the full [email protected] address.

Is it in anyway possible configure it (WHM, this specific cPanel account, etc.) to allow users to auth with only their username? It would make the migration process much less of a headache. :)

Please let me know if more information is required.



Staff member
Apr 11, 2011
Hello @CreateChange,

You must authenticate with the full email account username (e.g. [email protected]) because the mail server needs to know the full email address to determine which passwd and shadow files to read when validating the authentication details. Otherwise, conflicts would arise when entering user1 in cases where [email protected] is created for multiple domain names on the server .

The only exception to this rule is when you access the cPanel account's default address mailbox. In this case, you can login with the cPanel account username on it's own without the @domain.tld suffix.

Thank you.