[Mailman-Developers] Limiting copies of cross posts sent

[Christopher G. Petrilli]

On Fri, Jan 29, 1999 at 02:46:59PM -0600, Jeffrey C. Ollie wrote:
> > * Sendmail only does this under SMTP, not under anything else
> 
> Not if you add the 'm' flag to the delivery agent.  Then sendmail will
> invoke the delivery agent with multiple recipients specified on the
> command line.

Interesting, I've never seen this used for mailing lists, so I don't
know what to say... obviously this is a sendmail only thing that gets
into the whole problem outlined below.

> > So, that means that Mailman would have to accept its messages over SMTP,
> > which sin't in itself a problem... the problem is that as far as I've
> > been able to determine, sendmail can't be told to deliver SMTP mail to a
> > different port than 25.
> 
> Actually you can, see p522 in the 2nd edition of _Sendmail_ (section
> 30.4.1.2).

I stand corrected, although I will point out that this is burried quite
late in the sendmail world, and 5 people I know who relaly know sendmail
didn't know this :-)  Hense, it's obscure at best... Regardless...

> > That's not nearly as ugly as the problems with doing it ... also it'd be
> > different for every mailer, and quite different in many cases I think.
> 
> Yes, existence of multiple SMTP daemons is a problem in that we'd have
> to provide documentation on how  to modify the configuration for many
> different daemons.  However doesn't this already happen?  Aren't
> sendmail, exim, qmail, or whatever sufficiently different in their
> implementation that setup is already problematic?

Dunno, at least with sendmail/postfix, it's just trivial additions to
the /etc/aliases file.  I use the same ones for postfix as you would for
sendmail, absolutely, no exceptions.  I THINK EXIM behaves the same way,
and I think qmail does as well.  This is trivially simple, it's also how
every other mailer plugs into the MTA world. (Ialso run full blown
LISTSERV).

> Another, more radical idea would be to completely replace the regular
> SMTP daemon with a SMTP daemon written in Python that integrates
> directly with MailMan.  I've been considering doing that for another,
> more radical project that I have in mind.  The only problem with this is
> that you have to dedicate a box to running MailMan and there would be
> some performace issues, but I guess that this would be offset by the
> ability to run MailMan on a Windows or Mac OS system.

I'm not sure this is a plus, considering I want a REALLY reliable system
:-)  I don't have a problem with someone writing a Python MTA (I've
thought about it many times) BUT... mailman can't use it, at least in my
opinion.  Period.  The MTA has to deal with /etc/aliases files just like
everyone else, it's a defacto-standard at this point.

> The idea of using a database to filter out multiple copies would be
> problematic for sites that have high volume lists with a large
> subscriber base.  Just think of all of the storage that you'd need!

Actually, locality of reference fixes this is MOST cases... that is,
it's "safe" to assume for handwaving purposes that email originating
from userA will reach mailserverB in x time... that is the same for all
the different lists on X.  So it's reasonably safe to assume that
Mailman will see multiple copies almost simultaneously (i.e. no more
than 5 minutes?).  What this means is that you only have eto CACHE the
Message-Id information, not keep it forever.  And you're only keeping it
for cross-posted messages also, not everything.  I think this is totally
doable, with a decent caching mechanism. (probably in C code, added to
the normal Python distribution).

Chris
--
| Christopher Petrilli
| petrilli@amber.org