Whenever I see something that says "best practices" I can't leave it alone.
Derek Simkowiak writes:
I'm setting up an Exim-based mail server, with procmail as the
local delivery agent. Exim is an MTA (SMTP server). But I'm having some
confusion as to the relationship of the MTA to procmail.
Exim has built-in support for the .forward file -- my
understanding is that this is a feature 'inherited' (read: copied) from
Sendmail. However, the procmail man page says:
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Procmail should be invoked automatically over the .forward file mechanism
as soon as mail arrives.
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OK. There's this thing called finger. And if you finger an account, which
is more or less impossible for smaller or larger values of "impossible"
anymore, among other things it tells you is where mail is forwarded for the
account.
Finger and forward both date back to a time when people wanted to advertise
not only the disposition of their e-mail, but their work plan. Yes. Plan.
Finger shows you the plan. Yes, if you have finger support you can also
have a .plan. A .plan is supposed to allow people to see what you're up to,
for some large value of pi, in the sense that long strings of digits are
large. So going along with this is this .forward file, which has been
historically understood as instructions as to where mail to this account
should be delivered.
Procmail is a latecomer in this regard. You see, pagers and whatnot have
been around for a long time, for suitable boring values of pi. And it was
discovered that you needed some way to send stuff to them. The default way
to do this was instead of treating what was in the .forward as an extension
of an alias, to encapsulate it and execute it as shell. (wait, they did
this for aliases too, so....)
So. That was fun, wasn't it? And most people don't have a clue what I'm
talking about. Bet they don't have a .plan either, and why should they?
Indeed. So, they don't need no steekin' .forward, now do they?
Procmail just picks it up, automagically, if you have a .procmailrc. (The
Cobalt Qube is probably seminal in this regard.) But that's really not
procmail's fault, procmail itself does none of it.
If procmail is invoked by a .forward, that's hardly procmail's fault, now
is it? If procmail just happens to be invoked all of the time, that's
hardly procmail's fault either, is it? No, procmail is invoked. And you
need to start there. Otherwise you need to get really philosophical and
ask: "why is procmail invoked?", and the answers may astound you, or they
may numb your brain like too much rat poison or television.
And what you'll find if you don't chew your own leg off first is that some
MTA somewhere is either hard-coded or else configured to call procmail.
Does that mean I should disable Exim's support for the .forward
file? Or does that mean I should have procmail invoked as a pipe
command _via_ the .forward file?
In short, does procmail ever use or read the .forward file?
I am further confused by the next sentence:
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Alternatively, when installed by a system administrator, it can be invoked
from within the mailer immediately.
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It seems to me that this is saying the exact same thing as the
last sentence, and yet it says "alternatively".
I want users to be able to both (a) have mail forwarded to
arbitrary other accounts, and (b) use procmail to filter messages and take
recipe-based actions. Would that involve both the .forward file and the
.procmailrc? Or does that mean users would need to have a recipe in
.procmailrc to do any desired forwarding?
Any help (esp. examples) would be greatly appreciated.
Thank You,
Sorry, I can't help you. Somebody here may be able to help you, but that's
just because we're all in hell together. Really, the question you're asking
has nothing to do with procmail.
However, in the sense of "best practices", it should be answerable
everywhere. Per face isse. err... per fectus est? err.. I dunno.
Anyway: non sequitur. QEQ.
Derek Simkowiak
--
Fred Morris
m3047(_at_)inwa(_dot_)net
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