reply

REPLY  -   write and send a reply to one or more messages

Usage:  REPLY [message-sequence]
  Unless specified, the message-sequence is "current".

  The prompt "Send reply for message  to:" will appear.  Unless specified,
  "sender not-including" is assumed.  The options are:
      sender: the sender of the original message, only.
      all: everyone in the TO and CC fields of the original message.  
      none: don't send a reply (used to skip one of a set of messages).
  and also:
      including: include the original message in the reply.
      not-including: do not include the original message.

The REPLY command sends a reply.  It is similar to SEND, but the TO field
  is supplied from the FROM of the original; the SUBJECT field is copied;
  and a CC field may appear if you specify "all".  You then just type
  the text as in SENDing.  Your message will have an IN-REPLY-TO field 
  showing the date of the original message you received.
  
Examples: 
  To send a reply to the current message, message 25, to the sender, just
  use the defaults:  
    MM>reply				#current message, by default
     Send reply for message 25 to:   	#sender not-including, by default
     Message ... :
  To send a reply to message 10 (regardless whether it's "current"), to 
  all people who got the original message, and including the text of the 
  original message:
    MM>reply 10                           
     Send reply for message 10 to: all including
     Message ... :

For more help type "help" and one of these topics:
  message-sequence   send   addressing   message-handling   text-mode

For help about customizing REPLY, type "help set" and one of these topics:
  reply-all   reply-include-me   reply-indent   reply-initial-display   
  reply-insert