Hi nisamudeen97,
pls. be informed, that it up to the server administrator, to configure the log - level for the depending service log. If you need a more decent output in a service log, consider to choose a higher level, than the standard defined log - level for that service in the depending configuration file.
451 4.7.1 Service unavailable
This can be an indication of a non - working depending service, or a depending service, blocked by a firewall setting. Consider to restart
/etc/init.d/ctasd_initd restart
/etc/init.d/ctmilter_initd restart
/etc/init.d/pc-remote restart
... and pls. look out for possible issues in the depending log - file for further investigations and suggestions.
Often enough, the Plesk repair utility is able to resolve misconfigurations, so pls. consider as well to use the command:
plesk repair mail
... to repair issues with your mail - server.
An additional method to repair mail - server issues, is to switch between qmail and postfix and smtp-courier and dovecot. ( NO current eMail will be touched or deleted during this procedure! ):
/usr/local/psa/admin/bin/autoinstaller --select-product-id plesk --select-release-current --install-component qmail
( wait for the procedure to be finished, pls... )
/usr/local/psa/admin/bin/autoinstaller --select-product-id plesk --select-release-current --install-component postfix
/usr/local/psa/admin/bin/autoinstaller --select-product-id plesk --select-release-current --install-component courier
( wait for the procedure to be finished, pls... )
/usr/local/psa/admin/bin/autoinstaller --select-product-id plesk --select-release-current --install-component dovecot
If you need help with further investigations, pls. consider to post more informations from your mail - log, or/and syslog and consider as well to post the depending configuration file(s) from your used mail - server.