Binary package “pmailq” in ubuntu xenial

postfix mail queue manager

 pmailq parses the output of command from postfix (postqueue -p). It permits
 to perform some actions on a group of entries in queue (like removing or
 displaying them in a machine readable format). They are selected by applying
 filters (wildcards are allowed) on criterias like email address, error message
 from SMTP server, message size, mail status in queue.