MOVE  -  copy the current message into another mail file, and delete...

Usage:  MOVE [/type] filename  
  Unless specified, type is "/mbox".

Please note that MOVE acts on the "current message" in your mailfile, and
  -NOT- on the message you have just written.  If you are REPLYing, the 
  "current message" is the one you are replying to.  To save the message
  you are writing, see help for SAVE-DRAFT or FCC.

The MOVE command copies the message to another mail file, and deletes
  it in the current mail file (compare to COPY).  

If the mail file named exists, MOVE adds a copy of the message to the end 
  of the file.  If the mail file does not exist, MOVE creates it, unless
  the variable auto-create-files is set to NO.  If a directory is not 
  specified with the filename, MOVE assumes the MAIL-DIRECTORY, which by 
  default is your home directory. 
  
If a type is not specified, /mbox is used for new files and the existing
  type is retained for existing files.  Use the type /mbox unless you also 
  use another mail system that needs another format.  /babyl and /mtxt 
  are the other types. 

Example:               
    Send>move oldmail                #copies to a file named oldmail

For more help type "help" and one of these topics:
  copy   headers   set auto-create-files   set mail-directory
  set auto-create-files   set default-mail-type   set mail-directory
