save-draft

SAVE-DRAFT   -  save an outgoing message, to be continued later

Usage:  SAVE-DRAFT filename

The SAVE-DRAFT command saves an outgoing message to a file, so that you
  can continue to work on it later.  You can even log out and return to
  it on another day.  Use the command RESTORE-DRAFT at the MM> or Read>
  prompts to continue the message.

Example showing typical use; jonesletter is the SAVE-DRAFT file:
    Send>save-draft jonesletter
    Send>quit
  Then, at any later occasion, continue with:
    MM>restore-draft jonesletter

The SAVE-DRAFT and RESTORE-DRAFT commands use the directory defined in the
  MAIL-DIRECTORY variable unless you specify another directory.

For more help, type "help" and one of these topics:
  quit   filing   basic   set mail-directory    top-level-mode restore-draft