Creating a Distribution List
  A distribution list is a file that contains a list of users.
  Distribution lists are not created within Mail.  Use an editor,
  such as EVE, to create your distribution lists.
  When you create a distribution list, type one user name per
  line.  You can also include the names of other distribution
  lists by specifying an at sign (@) followed by the name of the
  distribution list.  Exclamation points (!)  delimit comments;
  Mail will ignore everything to the right of the exclamation
  point.  For example:
      !  PROJECT INTEREST DISTRIBUTION LIST
      OZ::NOLAN
      TUTTLE
      DARCY::MORRIS
      @PROJECT !PROJECT TEAM
  When naming distribution list files, use a DIS file type since
  that is what Mail looks for by default.
  Additional topics:
  *   Using a Distribution List