Description

   The DELETE command is used to delete one or more messages from
   the channel queue directories. The messages to be deleted are
   specified by their message identification numbers shown by
   the most recent DIRECTORY command. That number appears in the
   leftmost column of the DIRECTORY command listing. Ambiguous
   message numbers must be qualified by the proper channel name
   with the /CHANNEL qualifier.

   Note that the DELETE command irrevocably deletes each message
   it is instructed to delete: the messages are not returned to
   their originators nor will any further attempts to be made to
   deliver them to their recipients. The messages are permanently
   deleted. Often, it is preferable to use the RETURN command so as
   to return the message to its originator, (e.g., bounce it back to
   the sender).