POP3 configuration in Outlook and etc.

[Mindaugas]

Hello,
I have to provide full username@domain name in the "User Name" box to configure POP3 connection.
Is there possibility to workaround this? I want to provide only username.

Thank You.

[Mindaugas]

What I discover:
I have two domains and if I change Global settings -> General information -> Default domain -> to other domain I can configure mail client with only username. But of course I have to provide username@domain for old default domain.
It is workaround, but maybe there are other solution?