Edward Marshall answered my question,
| There are ways around this, but they all involve
| hacks to sendmail.cf (in the case of sendmail); what I've done in the past
| is export this information via environment variables to the LDA (such as
| the remote IP address).
And that's the problem: this needs a user-level solution. If I could change
sendmail.cf I could set procmail as the LDA and have it pass the suffix.
| QMail solves this in an extremely elegant manner: .forward becomes
| obsolete, replaced with .qmail-ext files (where "ext" is the extension you
| want).
Sendmail on the site where I'd like to do this honors ~/.forward+suffix
files, which supersede ~/.forward when the suffix matches. The drawback,
like .qmail-ext, is that you need to know in advance what suffixes might be
on your incoming mail and have .forward+suffix files ready for them. Also,
there's no way I've found for the .forward+suffix file to know its own name
the way a shell script or function has $0, so you can't save disk space in
your user account by linking a single .forward+suffix to many file names
and have it contain something like
"|/usr/local/bin/procmail -a $0"
and then pass $LOGNAME+suffix to .procmailrc as its $1.
| [qmail] also places "Delivered-To:" headers in each message for easy parsing.
| VMailer also solves this with the "Delivered-To:" header.
Yes; now that is ideal for a procmail user: text in the header, even on blind
carbons with other recipients on the site. There never would be other
recipients of a qmail delivery anyway, but I don't know whether VMailer works
that way.
| If this -is- sendmail you're dealing with, check on comp.mail.sendmail;
| they may have some unique solutions for you.
OK, I'll try there. I've looked into that newsgroup and everything I've seen
there is for people who administer sendmail on their sites (though of course
some of them are new to it and administering it on one-person sites for only
themselves).
| This definitely isn't a procmail-specific problem...you'd run into this
| with any LDA or filtering software.
True, but procmail can possibly do something with the information, unlike,
say, Elm's filter utility.
Thank you for the advice.