[imp] problem with imap authentication

[piyush at 550access.com]

hello 

  right configure the postfix mail server with virtual delivery agent(VDA) with
    Mysql database. 
    all the virtual domains are authenticated through courier-imap  with mysql
    database enable.
    postfix mail server is perfectly working with virtual domains with
    courier-imap.
    But i have problem with configuring the Horde-imp with postfix + courier- 
IMAP.
    
    i have face following error when I try to login.
    this is my horde log file.

    Aug 16 12:59:48 HORDE [notice] [imp] Login success for piyush at vipindia.com
    [192.168.254.224] to {mail.vipindia.com:143} [on line 83 of
    "/var/www/html/horde/imp/redirect.php"]
    Aug 16 12:59:49 HORDE [error] [imp] FAILED LOGIN 192.168.254.224 to
    mail.vipindia.com:143[imap/notls] as admin at vipindia.com [on line 282 of
    "/var/www/html/horde/imp/lib/IMP.php"]
    
    my courier-imap is working fine. I already test through 

    
    telnet mail.vipindia.com 143 .....
    
    [root at linuxserver config]# telnet mail.vipindia.com 143
    Trying 192.168.254.129...
    Connected to mail.vipindia.com.
    Escape character is '^]'.
    * OK [CAPABILITY IMAP4rev1 UIDPLUS CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT
    THREAD=REFERENCES SORT QUOTA IDLE ACL ACL2=UNION STARTTLS] Courier-IMAP
ready.
    Copyright 1998-2004 Double Precision, Inc.  See COPYING for distribution
    information.
    a login piyush at vipindia.com piyush
    a OK LOGIN Ok.
    
    please let me know anybody know the solution of this types of problem.
    
    regards,
    piyush