Dovecot-lmtp Connection refused

Issue : Mails are not delivering to Roundcube OR any other webmail and the Logs showing the following error.

======================================

Oct 16 19:27:45 server.example.com postfix/error[30545]: DF7YHSA90: to=<admin@example.com>, relay=none, delay=924, delays=924/0.13/0/0, dsn=4.4.1, status=deferred (delivery temporarily suspended: connect to mail.example.com[private/dovecot-lmtp]: Connection refused)

======================================

Cause : “lmtp” protocol not correctly enabled on the server

Fix : Please go the “/etc/dovecot” and search for all the files for the string “protocols”.

Command and Output :

Please make sure that lmtp is enabled /etc/dovecot/dovecot.conf as given below.

======================================

protocols = imap lmtp

======================================

Also make sure that there is no duplicate entries added in other files.