Some mail systems, such as SNADS mail systems, cannot handle real RFC 822 (Internet) addresses. Typically, one must set up algorithms or table lookups to translate between the real RFC 822 addresses, and addresses that can be used on the SNADS side. So that one does not need to register all possible addresses (the entire Internet) in advance, when sending to such mail systems, it may be useful to autoregister addresses; that is, when a previously unseen address appears in a message, automatically generate a translation address for it.

Autoregistration is enabled using the forward database, reverse database, and the special flags $A and $F in the REVERSE mapping table.

Typically, the autoregistration is only to be performed for messages going out special channels such as SNADS channels, therefore typically a channel specific reverse database and channel specific REVERSE mapping table should be used. If a non-channel specific reverse database was already in use, note that it is not usually necessary to make the entire reverse database channel specific. Instead, it is usually possible to continue using the former non-channel specific entries in the reverse database, as well as the additional new channel specific entries; see below.

The components of setting up autoregistration of addresses are as follows.

1. Enable use of the forward database. Set bit 0 (value 1) for the PMDF option USE_FORWARD_DATABASE. A general discussion of PMDF options and the PMDF option file, option.dat, may be found in Chapter 7.
2. Ensure that a forward database exists. If you do not already have a forward database, then you must create one with the PMDF CRDB (OpenVMS) or pmdf crdb (UNIX or NT) utility. e.g., on OpenVMS:

   $ PMDF CRDB/LONG_RECORDS NLA0: PMDF_FORWARD_DATABASE

   or on UNIX:

   # pmdf crdb -long_records /dev/null PMDF_FORWARD_DATABASE # chown pmdf /pmdf/table/forwarddb.*

   or on NT:

   C:\ pmdf crdb -long_records nul PMDF_FORWARD_DATABASE

3. Ensure that a reverse database exists. If you do not already have a reverse database, then you must create one with the PMDF CRDB (OpenVMS) or pmdf crdb (UNIX or NT) utility. e.g., on OpenVMS:

   $ PMDF CRDB/LONG_RECORDS NLA0: PMDF_REVERSE_DATABASE

   or on UNIX:

   # pmdf crdb -long_records /dev/null PMDF_REVERSE_DATABASE # chown pmdf /pmdf/table/reversedb.*

   or on NT:

   C:\ pmdf crdb -long_records nul PMDF_REVERSE_DATABASE

4. If a new pseudo host or domain name will be used for autoregistration purposes, ensure that the other mail system knows to route that pseudo host name to the PMDF system. SNADS systems need routing information for any new pseudo host name you will be using in the autoregistration.
5. Create a PMDF sequence number file for use in the autoregistration. The typical way to generate unique usernames for autoregistration is to use a PMDF sequence number file. In order to use a PMDF sequence number file for such a purpose, you must first create one; see Section 5.3.2.6 for additional details. e.g., on OpenVMS:

   $ CREATE/FDL=PMDF_COM:sequence_number.fdl PMDF_TABLE:autoreg.dat

   Or on UNIX:

   # su pmdf % touch /pmdf/table/autoreg.dat

   Or on NT:

   C:\ copy nul C:\pmdf\table\autoreg.dat

   If you prefer to use some other mechanism, say provide your own image which the REVERSE mapping will invoke, that is another option, in which case you will not need such a sequence number file.

6. Put the entry or entries triggering autoregistration into the REVERSE mapping table. If you do not already have a PMDF mappings file, then you must create one and to it add a REVERSE mapping table with entries for performing the address autoregistration. (A general discussion of the PMDF mappings file may be found in Chapter 5; a discussion of the REVERSE mapping in particular may be found in Section 3.3.2.) There will be two forms of entries, the first form blocking autoregistration of any addresses which should not be autoregistered (such as native SNADS addresses), and the second form performing the autoregistration of any other addresses. Each entry blocking autoregistration will have the general form

   *|dest-channel|orig-address $N

   while each autoregistration entry will have the general form

   *|dest-channel|orig-address $Y$A$Freplace-address

   where replace-address is an address with which to replace the real RFC 822 address. For instance, when sending to SNADS, which is limited to an eight character username and an eight character pseudo host name, a typical sort of approach might be to generate eight character pseudo usernames using a PMDF sequence number file, and use a fixed pseudo host name, say INTERNET. For instance, assuming that SNADS hosts are SNADS1, SNADS2, etc., then on OpenVMS:

   REVERSE *|snads_*|*@SNADS1 $N *|snads_*|*@SNADS2 $N ! ...etc... *|snads_*|* $Y$A$F$#PMDF_TABLE:autoreg.dat|16|8#@INTERNET

   or on UNIX:

   REVERSE *|snads_*|*@SNADS1 $N *|snads_*|*@SNADS2 $N ! ...etc... *|snads_*|* $Y$A$F$#/pmdf/table/autoreg.dat|16|8#@INTERNET

   or on NT:

   REVERSE *|snads_*|*@SNADS1 $N *|snads_*|*@SNADS2 $N ! ...etc... *|snads_*|* $Y$A$F$#C:\pmdf\table\autoreg.dat|16|8#@INTERNET

7. If you want to continue to do non-channel specific reverse database reversals for other addresses, change the $N blocking entries shown above to use $Y$D to cause the addresses to be passed back for a reverse database lookup, plus add a final REVERSE entry to cause any other addresses to be passed back for a reverse database lookup. For instance, on UNIX:

   REVERSE *|snads_*|*@SNADS1 $Y$D$2@SNADS1 *|snads_*|*@SNADS2 $Y$D$2@SNADS2 ! ...etc... *|snads_*|* $Y$A$F$#/pmdf/table/autoreg.dat|16|8#@INTERNET *|*|* $Y$D$2

   Note that these $Y$D entries are passing back only the original address for the reverse database probe, and omitting the channel specific information.

8. Make the reverse database and REVERSE mapping lookups channel specific. Set the PMDF option USE_REVERSE_DATABASE=29.
9. Recompile, if necessary, and restart PMDF components. If using a compiled PMDF configuration, recompile (and on OpenVMS reinstall) it. Restart any resident process components of PMDF, e.g., the SMTP server and the SNADS and PROFS processes.