Description

   The SUBSCRIBE command adds either your address or a specified
   address to the specified mailing list. A response message
   reporting the success or failure of the subscription request will
   be returned. If the file PMDF_MAILSERV_MAIL_DIR:list-name.TXT
   exists, it will be sent to you.

   Use the UNSUBSCRIBE command to subsequently unsubscribe from a
   mailing list; use the DIRECTORY/LIST or LISTS command to obtain
   information on available mailing lists.

   Note that some mail servers can impose restrictions as to who may
   or may not subscribe to a given list.