headers

HEADERS  -  display the header (one-line summary) of the current message

Usage:  HEADERS 

The HEADERS command shows a one-line display for the current message with
  the sequence number, date, sender, subject, status and length.

In the display, the letters at the left indicate the following:
  A:answered (replied to).  D:deleted.  F:flagged.  K:contains a keyword.
  N:new (unseen and recent).  R:recent (arrived during this MM session).  
  U:unseen (never read).

For more help type "help" and one of these topics:
  basic   reply   delete   flag   keyword   mark   check