I have configured /etc/dovecot.conf file .
The cahnges made are
#protocols = imap imaps line no:14 added

protocols = pop3 pop3s

# login = imap line no:84
when i restarted the service the errors which i got are

service dovecot restart
Stopping Dovecot Imap: [FAILED]
Starting Dovecot Imap: [ OK ]

Again,

service dovecot restart
Stopping Dovecot Imap: [ OK ]
Starting Dovecot Imap: Fatal: listen(143) failed: Address already in use
[FAILED]
Kindly give a solutions for this.This is the first time i am working with dovecot.
thank you

Some service on your server is already using port 143. Use netstat to find out which service is running on you're port 143.. and shut that service down if you don't need it.