[CentOS] Postfix login Name Error

Wed Sep 5 04:48:20 UTC 2012
jiten jha <jitenjha11 at googlemail.com>

Dear Friends,

I have done basic postfix mail server configuration but problem is when I
try to login then it is not taking my name . it is taking full name with
domain name.
My domain name is *"studen.ac.in"*
My user name is jiten when I try to login with my name in a log it is
*" Sep  5 10:06:56 neu dovecot: imap-login: Aborted login (auth failed, 1
attempts): user=<jiten at ac.in>, method=PLAIN, rip=,
lip=, secured "*

But when I try to login with* jiten at student.ac.in *it is working fine . So
please help me how can I remove or hide my domain name when I and other
user want to access my mail server .

Thanks & Regards
Jitendra Jha