Here’s a list of stuff I user everyday and other email admins will also be using, Let me know if I missed anything
List/Print current mail queue
# postqueue –p
# mailq
If it’s a huge que, you can pipe it with tail
# mailq | tail
Flush the queue
# postqueue -f
Schedule immediate delivery of all mail that is queued for the named as domain.come.
# postqueue -s domain.com
TO delete all queue
# postsuper -d ALL
To delete a particular message
# postsuper -d messageid
Reque the mail or resend particular mail
#postfix -r msgid
To find mail version
#postconf -d mail_version
mail_version = 2.6.6
You can also follow the steps in the link below which is the most simple and well explained documentation available with regards to Configuring postfix.
