Mail coming from wrong domain

When I login (to Squirrelmail) with user 'test', who is a mail user in domain vhost.vdomain.com & send an email, it appears to come from the right user, but it comes from realhost.realdomain.com.

If I were to switch to Uebimiau, would it fix this problem, or is there something I am missing?

 

You must configure the correct sender email address in your client (Squirrelmail, Uebimiau, ...).