How to manage sendmail queue
To check the main queue (/var/spool/mqueue):
To check mail submission queue (/var/spool/clientmqueue):
# mailq -Ac
To flush the queue (attempt to deliver all queued mail):
# sendmail -q -v
Add -Ac flag to work with submission queue.
Sendmail doesn't have commands to manage the queued messages. In order to delete a message you have to cd to corresponding directory and rm the file.
mailq is identical to sendmail -bp.