Thanks for the reply, i have reinstall ispconfig but after reinstallation, fails to start with this error :
[root@mail install]# /etc/init.d/dovecot start
Starting Dovecot Imap: Error: Error in configuration file /etc/dovecot.conf line 715: Unknown protocol name (section changed in /etc/dovecot.conf at line 709)
Fatal: Invalid configuration in /etc/dovecot.conf
The php version is 5.1.6
Thanks a Lot!
Have a Good Day