Postfix command

postfix flush
postfix -f

To flush (resend) mail from queue

mailq

To see mail queue

postsuper -d ALL

To remove all mail from the queue

postsuper -d ALL deferred

To remove all mail in the deferred queue

Postfix delete script.
Download this first postfix-delete.txt
Then rename it to "postfix-delete.pl"

./postfix-delete.pl spamdomain.com

Delete all queued messages from or to the domain called fackspamdomain.com, enter.

./postfix-delete.pl xyz

Delete all queued messages that contain the word "xyz" in the e-mail address.