Default domain for logged in users

Hello

Is there a way to setup a default domain for the logged in users? for example, if someone logins as "myusername", the webmail automatically appends a domain to the username, staying like "myusername@defaultdomain.com"...

This is important because my IMAP server accepts logins without domains, it will just assume a default domain... and it will also cause some problems with the contatc list, because if you login with "mysername" and later on with "mysername@defaultdomain.com", it will create two different users on the database with two different contact list, but everything else would work fine..

thanks in advance!

p.s.: EXCELLENT WEBMAIL! VERY IMPRESSIVE! CONGRATULATIONS!