🚀 go-pugleaf

The purpose of this is, of course, to be able to handle mail addressed
to users on some host, where many (but not all!) of those "users"
actually have their accounts on another host, without having to set up
individual aliases or .forward files for them. It is a requirement that
it also works for local mail, i.e. sent to just 'user'.

I thought it would be simple, having seen (but never used:-) an attempt
at implementation in some old sendmail.cf. E.g., assuming only a normal
"stupid" sendmail, define a class L containing all locally known names
(aliases + userids), and then replace the normal selection of the local
mailer with:

R$=L			$#local $:$1			known local names
R$+			$#ether $@$N $:$1<@$N>		forward unknown names

where $N is the name of the host to forward to.

This works as a first approximation, but falls flat on its face in the
presence of e.g. a not uncommon .forward file:

\user
"|/usr/ucb/vacation user"

When these adresses in turn are passed trough the rulesets, neither
matches the $=L, and so they incorrectly get forwarded. There are two
problems here, the one of identifying mail to files and programs might
be solved by explicitly matching / and |, but I can't see a way to deal
with quoted addresses (including those where the file/program is inside
quotes).

My next idea was some kind of "wrapper" for the local mailer, which
could weed out the unknown users and feed them back to sendmail with the
appropriate @host tacked on. Naively, I thought this would have the
added benefit of sendmail taking care of aliases/files/programs,
obviating even the need for the U class above - but as I should have
known, sendmail also takes care of the unknown users...

I'm beginning to think this is really impossible with a "stupid"
sendmail, and perhaps even with IDA (looking through some of the
comments in the IDA Sendmail.mc regarding MAILSERVER - which is *not*
what I want to do, but it has similar problems) - but I would be happy
to be shown otherwise...

Thanks
--Per Hedeland
per@erix.ericsson.se  or
per%erix.ericsson.se@sunic.sunet.se  or
...uunet!erix.ericsson.se!per