16 Mail routing

 This is one of the most complex parts of FrontDoor and takes
 considerable time to learn and understand. Make sure you understand
 how each routing verb affects mail routing before you use it.

 When FD is brought up, it scans for any active events and when one is
 found, opens the route file, ROUTE.FD, and uses it to determine whom
 to send mail to, and how to send it. The route file must be placed in
 the SYSTEM directory. If the timestamp of the route file is modified,
 FD will detect it and re-scan the NetMail folder (see "Semaphores").

 Global routing verbs are those that appear before any SCHEDULE
 keyword in the route file. They are always used, so you can specify
 routing that is identical for all your events here.

 Local routing verbs are those that appear between two schedule
 keywords (a schedule block) in the route file. FD determines which
 schedule block to use by searching for a schedule keyword with a tag
 (letter) matching the current event tag (see "Events").

 Several references are made to Hold status in this chapter. Do not
 confuse this with the HOLD route verb. The Hold status refers to the
 message status bit (see "Message Status Bits"), or where stated, to a
 system's nodelist status.

 FD allows you to insert comments in your route file. Every line with
 a semicolon as the first non-space (TAB/Space) character is treated
 as a comment. While comments may seem inadequate at first glance, it
 is a very useful function. Going back to a route file you wrote five
 months ago may not be your definition of spending a weekend in joy
 and happiness.

 Addresses specified in the route file should always be fully
 expressed. The * macro (implying "ALL") is supported. You can also
 use nodelist flags to specify a range of systems. The routing
 language is completely case insensitive (case does not matter).
 SCRIPT, SCripT, and scRIPt are all treated as the same command.


     16.1 Default routing

     FD has several default rules for routing that will be used if no
     other rules have been defined for a specific system. Some of the
     default rules cannot be overridden by routing verbs.

     16.2 Message status

     Messages with immediate (IMM hereafter), Crash, File/Update
     Request, and Direct status will normally not be routed. They are
     sent directly to the destination system, with the exception of
     systems without a telephone number, as described later.

     Messages with IMM or Crash status can never be held by using the
     HOLD keyword. Messages with Crash status can, however, be
     prevented from being sent by event behavior, qualification lists,
     and cost restrictions, but never held with the HOLD route verb.

     Messages with Hold status will NEVER be packed into a mail
     packet. They can always be picked up by the destination system.
     Messages to points with Hold status can and will be picked up if
     the Boss of the point calls to pickup mail, unless the message
     also has Direct status.

     Messages with IMM status will always be packed into mail packets,
     overriding ANY event restrictions. If you have a message with IMM
     status, FD will add all other qualifying messages to the same
     system to the same mail packet.

     Messages with Received (read), Orphan, Lock, and/or Sent status
     are ignored by FD.