[CentOS] postfix login problem

Thu Sep 20 07:46:53 UTC 2012
jiten jha <jitenjha11 at googlemail.com>

Dear Friend,

I have postfix mail server. I open my mail server and put my username = jha
and password= 123456 it is giving my error "*ERROR*Unknown user or password

and In a log it is showing

-- Sep 20 13:03:22 neumann dovecot: imap-login: Aborted login (auth failed,
1 attempts): user=<jha>, method=PLAIN, rip=, lip=,

but When I put username = jha at XXX.ac.in so it is allow me to login in mail
server .

Why it is taking full Domain Name .

I want like gmail and yahoo when we open it they just ask for username and
password not full domain name.

Please help me..

Thanks & Regards
Jitendra Jha