====== PostFix ======
Command to view, force send and delete queues

|View Queued messages|mailq|
|Delete all Queued messages|postsuper -d ALL|
|Force sending mail|sendmail -q|
|View Message content in Queue|postcat -q <Queue Id>|

Reference: http://www.cyberciti.biz/tips/force-sendmail-to-deliver-a-message-in-sendmails-mail-queue.html