duplication of messages via mail gateway

[Russ Allbery]

I'm sorry it's taken so long for me to reply to this message.  I'm afraid
that this isn't likely to be that helpful at this point, but just in
case....

Erik Klavon <erik at eriq.org> writes:

> I've confirmed complaints from a user about duplicate messages sent to a
> mailing list which is bidirectionally gatewayed to a local
> newsgroup. The duplicates only appear on the mailing list (they are
> prevented on the newsgroup by mailpost's checking of the message
> id). When someone posts to the mailing list, the message is processed by
> mailpost and then posted to the local group. This then results in
> news2mail sending the message back to the mailing list. In an attempt to
> solve this problem, I decided to use distributions. Each message posted
> via mailpost is given a particular distribution:

> ucb-example: "|/usr/local/news/bin/mailpost -d ucb ucb.exmaple"

> Newsfeeds entries have been modified to not feed messages in the 'ucb'
> distribution:

> n2m!/ucb-agate-mailpost:!*:Tc,Ac,Wn*:/usr/local/news/bin/news2mail
> temp-example at agate.berkeley.edu:!*,ucb.example/!ucb:Tm:n2m

> After reloading the newsfeeds file, this modification still generates a
> duplicate! I've verified that the article posted via mailpost has a
> distribution header with a value of 'ucb'. I think I've read the man
> pages right and am not sure where I've gone wrong. (I'm using a cvsuped
> version of 2.3.4).

Can you confirm that the article is actually sent to temp-example from the
~/log/news log file?  The log entry for that message should indicate
whether or not it's been sent to that site.

> (I've fixed this problem another way by hacking mailpost to munge the
> path of the message, and then filtering out that path in newsfeeds as
> shown above. I'd rather not have to make this modification to mailpost,
> so I'd like to find out if this same effect may be achieved via
> distributions.)

This is a somewhat better way of handling this problem, IMO; maybe we
should add a flag to mailpost that adds a line to the Path header and
bless this solution?

What I do with our local gatewaying at Stanford is add an X- header that
then marks the messages as not to be gated back into mail.  But I'm not
using mailpost, and I'm not sure mailpost can do that.  (At some point, it
would be nice to clean up mailpost, but I probably won't tackle that any
time in the near future.)

-- 
Russ Allbery (rra at stanford.edu)             <http://www.eyrie.org/~eagle/>

    Please send questions to the list rather than mailing me directly.
     <http://www.eyrie.org/~eagle/faqs/questions.html> explains why.