FBB Recording a message

A message can be left by a user or within a forwarding connection. The
recording mechanism is always the same.

 The recording command is always like :

 Sx desti @ bbs < exped $ ident + filename

 Only recipient field is mandatory, all other fields are optional.

 Appending a filename is a possibility reserved to the sysop. The name must
be complete, including logic unit and complete path (C:\FBB\SYSTEM\TEST.TXT).

 When receiving the command line, a first test checks if a route exists when
a route has been specified, or if the message must be automatically routed
when no route was specified.

 The title of the message is then asked to the user.

 If the title is a missing, the message is canceled and the user returns to
the main menu.

 The text of the message is then asked to the user.

 The software checks possible preamble lines. These lines give information
on the previous BBS having routed this message. They all begin by R: on first
column. The BBS callsign is given behind the @ character within the preamble
line. All adjacent BBS mentioned in this preamble will be included in the
"already forwarded" list, and will not be concerned by this message. This
list specific to each message can be displayed with the $ or FN command
followed by the message number.

 When receiving a /EX in first column, or a Ctrl Z, a message number is then
assigned, The BID (or MID if private) and the list of adjacent BBS concerned
by this message are created. All these information are sent to the user when
acknowledging the message.

 In case of disconnection before the /EX or Ctrl Z, the whole message will be
lost, and the texts already stored are deleted.

 All information about the message (sender, recipient, route, MID, title,
etc...) are stored in the DIRMES.SYS file. The text of the message is stored
in a sub-directory of the MAIL directory. The sub-directory is MAILn where n
is the last digit of the message number. The name of the file corresponds to
the message number 123 is M_000123.MES, the number is 6 digits wide, in this
case it is in the sub-directory MAIL3.

 The message number uses a long integer (32 bits), the number boundary is
very far (more than 4 billions !).