Columbia MM
R> Read Mode

mark

MARK  -  mark the current message as seen without reading it

Usage:  MARK

The MARK command marks an UNSEEN message as SEEN.  It is very rarely
  used in READ MODE, since normally the current message already was
  SEEN.  

For more help type "help" and one of these topics:
  message-tagging   unmark   headers
message-tagging | unmark | headers | MM Home