Path: utzoo!mnetor!uunet!husc6!mailrus!nrl-cmf!ames!necntc!linus!heart-of-gold!jc
From: jc@heart-of-gold (John M Chambers x7780 1E342)
Newsgroups: comp.mail.uucp
Subject: Re: Rerouting of explicit paths
Message-ID: <132@heart-of-gold>
Date: 24 Mar 88 20:14:35 GMT
Distribution: na
Organization: Mitre Corp, Bedford, MA, USA
Lines: 58
Keywords: simple

> I think that Mark's proposal is OK but like a similar proposal I made a
> while back, I think it only applies to sites with the source to their
> mailer and I would guess they are in the minority.

Nah, you don't always need the source.  If you are running uucp, it's
pretty easy to do what I've often done:

	su	# Always useful (;)
	mv /bin/rmail /bin/rmail.real
	vi /bin/rmail
	...
	chmod +x /bin/rmail

The script you put in to replace rmail gets the recipient(s) as args,
and the message is on the standard input.  You can do with these as
you wish.  I usually do something like:

	SMARTHOST=rutgers!seismo!ihnp4
	# First, put the message into a named file.
	cat >/tmp/Mail$$
	# Next, learn what we can about the recipients.
	echo  'To: "$*           >/tmp/To.$$
	grep '^To:" /tmp/Mail$$ >>/tmp/To.$$
	...
	[Assorted lookups and recipient-munging]
	[Leave list of recipients in $*]
	...
	for r
	do	# Try a list of mailers for each recipient.
		...
		if [ $? -ne 0 ]; then
			# As a last resort, hand it back to uucp mail.
			/bin/rmail.real $r </tmp/Mail$$
		fi
		if [ $? -ne 0 ]; then
			# Bounce failed mail to a smarter mailer.
			/bin/rmail.real $SMARTHOST!$r </tmp/Mail$$
		fi
		if [ $? -ne 0 ]; then
			(echo "Can't deliver to "$r":"; cat /tmp/Mail$$) |mail Postmaster
		fi
	done
	rm /tmp/Mail$$

It's easy enough to make /bin/rmail into a general-purpose gateway between
multiple mailers.  You just hand each recipient to each mailer in turn.  It's
easy to include multiple database lookups, for instance.

You'd think that the real hackers out there would love uucp mail, because
it is so easy to modify it do do any of your favorite email tricks.  Of
course, if you have the source, it's even more fun...


-- 
[Send flames; they keep it cool in this lab :-]

Am I the same John Chambers as jc@minya?  You decide....
Hint:  That guy over at ut-sally is an imposter.  (;-)