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Re: What use /etc/procmail?

2001-03-16 16:46:20
At 16:15 2001-03-16 +0000, Trevor Jenkins wrote:
All the recipes I've seen here (or elsewhere on the 'net) appear to be
personal. There's little, if any, mention of how useful /etc/procmail can
be. The man page only says that procmail will use /etc/procmail before it
uses $HOME/.procmailrc.

It is my belief that those who would utilize procmail in /etc/procmail are going to be people who realize the dangerous potential it has if they implement something incorrectly there, and since only the sysadm can produce such a file, it doesn't apply to the average user. These two factors combined mean that only those who become familiar with procmail should actually employ /etc/procmailrc, and by that time, they'll have developed an understanding of it's usefulness.

My opinion only.

So I'm left wonder how useful is /etc/procmail. Will it be used when any
email message arrives and how much can I have it do before a user
account's .procmailrc is invoked?

Uh, about as much as you choose to toss in there. Besides system mail delivery tweaks, popular things to do are attachment cleaning and virus checking (ditching messages known to be viral for instance), which benefit even those users who don't have .procmailrcs (including those who don't have shell access and are simply POP mail clients). A handful of well-written recipes in /etc/procmailrc can reduce some sysadm nightmares significantly.

For example, can I use /etc/procmail to rewrite email that would not
normaly be accepted here because the addressee is neither an extant
username or a valid alias?

No. This is a job for the MTA. By the time procmail is invoked by the MTA, the local username the message is to be delivered to should be known. If it isn't, then the MTA will bounce the message, not invoke the LDA (Local Delivery Agent -- which is procmail, if so configured).

Some of my non-computer-literate friends get my
address wrong (typically putting an extra period at the end of my name) so
could I have recipes in /etc/procmail that correct their mistakes by
re-writing the header? Or am I fitting a lossing battle because sendmail
will have already bounced it back?

Depends on how sendmail (the MTA) is configured. If you're running a virtual domain configuration, you can have sendmail configured to pass *(_at_)domain(_dot_)tld mail to a specific local user, in which case, if the server received it, it'll get to you (no procmail config necessary). OTOH, that also means that blatantly incorrect addressing (popular on SPAM) will also deliver. The flip side is that if the MTA is not configured for wildcard delivery, then the message will bounce during the SMTP transaction - procmail won't be invoked.

I suggest you upgrade to smarter friends who can cope with email addresses or resend things to the PROPER address when they get a regular system bounce. <g>

---
 Sean B. Straw / Professional Software Engineering

 Procmail disclaimer: <http://www.professional.org/procmail/disclaimer.html>
 Please DO NOT carbon me on list replies.  I'll get my copy from the list.

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