[imp] Mail regarding IMP problem

[gms]

Dear All,
I have tried to get of horde/imp up and running since
yesterday evening, but to no avail.

The problem is this; after entering login/passwd I immediately get
returned to the login screen with errormsg "Login failed for some
reason. Most likely your username or password was entered incorrectly."

I am using two server one is mailserver & another is web server. I configure horde/imp in my web server.I am confused about my imap server , is it the name of mail server or web server?
say my mail server name is mail.test1.com and webserver name is gms.test1.com 
I am using: 
IMAP server= mail.test1.com
maildomain= test1.com
smtphost=mail.test1.com    
&
vi horde.php:::
 
$conf['auth']['params']['dsn']='{mail.test1.org/imap:143} INBOX';
 
I am confused about above configuration. 
 
 
I am running RedHat 7.2 with apache, mysql, imap, php all from rpms, and using horde-2.1 and Imp-3.1.

Please let me know the problem in my side and the exact solution that I can work.
 
Regards,
 
GMS
System Manager
IWM