Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!killer!ames!pasteur!ucbvax!ucsd!ucsdhub!hp-sdd!ncr-sd!ncrlnk!ncrpcd!wright!jsloan@wright.UUCP
From: jsloan@wright.UUCP (John Sloan)
Newsgroups: comp.mail.uucp
Subject: Re: Sendmail and pathalias
Message-ID: <287@thor.wright.EDU>
Date: 26 Aug 88 15:53:26 GMT
References: <13206@mimsy.UUCP>
Sender: news@wright.EDU
Reply-To: jsloan@wright.UUCP
Lines: 59

From article <13206@mimsy.UUCP>, by chris@mimsy.UUCP (Chris Torek):
	:
> Just as another note, it is possible to do this without modifying
> sendmail, although the method can only be described as a kludge.
> (Since sendmail refuses to distinguish between incoming mailers, the
> situation is even kludgier than it would have to be.)  What you do is
> have sendmail `deliver' everything to a program that does the routing,
> then hands the message back to sendmail for *real* delivery.
	:

It may be a kludge, but it's a worthwhile, and powerful, solution.
We've been using, since December 1986, a program we developed,
"dnagent", that does just this. Here is a portion of the man page.
(Apologies: I posted an earlier response to this which included the
entire man page. When I realized how long it was I tried to cancel the
article. I think I succeeded.)

     The Domain-Network Agent is an middle-end  to  the  Sendmail
     program.  When  Sendmail  identifies  a host or organization
     domain which it cannot resolve internally, it  delivers  the
     message  to the Dnagent mailer. Dnagent resolves destination
     addresses by querying  a  DBM  database  containing  rewrite
     strings  for  a key which matches the host-domain portion of
     the address. If a match cannot be found, Dnagent retries the
     query  with  the next higher order portion of the domain (if
     one exists), scanning from left to right. If a match  cannot
     be  found before the address is exhausted, Dnagent can fetch
     a default rewrite string from the database.

     This rewrite string  is  applied  only  to  the  destination
     address(es)  on  the outer envelope as specified by Sendmail
     as arguments on the command line when it forks and  executes
     the  Dnagent  mailer.  Addresses  in  the  RFC822  compliant
     headers in the text of the message are passed through undis-
     turbed.

     Rewrite strings may contain macros which are expanded to  be
     the  user  portion  of the address, the domain portion, that
     part of the domain which  matched  a  key,  and  conditional
     expansions which depend upon whether the full domain and the
     matched key are the same.

     Once the addresses are rewritten, Dnagent resubmits the mes-
     sage,  with  the new outer envelope, to Sendmail for further
     processing.  Several iterations may be made  until  Sendmail
     recognizes  an  address  which it can resolve. The number of
     iterations can be tuned by adding additional rulesets to the
     Sendmail  configuration  file,  or  by  making  the  rewrite
     strings in the Dnagent database more explicit.

     When different switches are applied to the  Dnagent  mailer,
     the  same  program may build, append, and dump the database.
     The database  entries  are  derived  from  several  sources:
     tables  available  from  the  CSNET  Info Server, the USENET
     Pathalias database, and local entries.
John Sloan    +1 513 259 1384    Wright State University Research Center
jsloan%wright.edu@csnet-relay   3171 Research Blvd., Kettering, OH 45420
..!ucsd!ncr-sd!ncrlnk!ncrpcd!wright!jsloan    ...!osu-cis!wright!jsloan
Logical Disclaimer: belong(opinions,jsloan). belong(opinions,_):-!,fail.