Displays a list of the messages in the current mail file,
    including message number, sender's name, date, and subject.

    Mail creates a new set of selected messages every time you use
    any of the following qualifiers:

       /BEFORE
       /CC_SUBSTRING
       /FROM_SUBSTRING
       /MARKED or /NOMARKED
       /NEW
       /SINCE
       /SUBJECT_SUBSTRING
       /TO_SUBSTRING

    Format

      DIRECTORY  [foldername]