how do I remove a message from the queue?

[Peter Brezny]

Someone sent a message with a 15 megabyte file attached.  qmail was able to
receive the message, but is now unable to perform local delivery since the
/var file system is full.

How can I purge that message from the queue?

I can locate where the message is, /var/qmail/queue/5/542, but am I going to
cause problems if I just delete the file that contains it currently?

TIA

Peter Brezny
SysAdmin Services Inc.