[horde] horde on local

[Mohsen Pahlevanzadeh]

Dear all,
I will want to present horde,qmail,vpopmail & dovecot for my the boss.
I have installed qamail,dovecot,vpopmail & horde groupware webmail
edition.
My boss has told me that i create many domain in my
computer(virtualdomain) & send mail from them.Dear all,i didn't have
Public IP.my host name is debian.localhost.I created x & y domain in
vpopmail & qmail.But when i send an email from user at x email address to
user at y, it send my email as user at x.debian.localhost,thus i can't receive
this email in user at y's inbox.
Please guide me that i remove debian.localhost from horde.I want horde
work with just mydomain  , not mydomain.debian.localhost 
Yours,
Mohsen