I recently had to research the source of some email issues which required me to check what may still be in a queue for sendmail. Since the source of the email was PHP, which was using the default mail method, the emails would be going through sendmail.

To check the queue, I used:


# mailq

(this checks /var/spool/mqueue, the primary queue)


# mailq -Ac

(this checks /var/spool/clientmqueue, which may or not be used on your server)

Unfortunately my queues were empty, but these commands will be very helpful to me in the future.