On Wed, 2005-11-30 at 12:35 -0500, Dick St.Peters wrote:
This is NOT rare, at least not here, and I don't think my service is
unusual in this respect.
I didn't say it was rare to receive mails with multiple recipients. I
said that _one_ of your options was to recogise that it's going to be
relatively rare to receive mails which have multiple recipients _AND_
where the desired outcome of different recipients is different.
What I used to do to address this was limit the number of recipients
per envelope to one at my border MTAs. Each message can then be
processed according to the acceptance criteria if its one recipient.
Yes, that was another of the options I outlined.
(After discovering that some spammers detected this and did RSET after
RSET, apparently automated, to generate separate envelopes, I added
limiting the number of envelopes per SMTP connection to one. This is
RFC-dubious if not outright RFC-disallowed, but it's very effective.)
Not a great deal more effective than just making separate connections,
and not relevant to the question of giving different outcomes for
different users. In fact, it's precisely what you try to achieve if you
deliberately restrict senders to one RCPT at a time.
If you don't like bogus bounces, implement SRS or SES for all your
outgoing mail. That way you'll know which bounces are of mail you
actually sent and which are fake after RCPT.
Er, yes. I've been doing that for a _long_ time -- mine was the original
implementation (in Exim) which led Meng to first coin the term 'signed
envelope sender'.
http://www.infradead.org/rpr.html
For a mail system handling any volume, MXs aren't just for "backup",
they are basically for load balancing.
Not sure I see the relevance in this case; multiple primary MX hosts
would presumably have the same filtering in place anyway. I was
specifically talking about MX _backup_.
Once you decide to reject at SMTP whenever possible, you have to do AV
scanning, anti-spam scanning, and all other acceptance processing on
the fly. This quickly means a single-server setup is overwhelmed for
even a small multi-domain mail service.
Running mail responsibly is hard; let's go shopping?
Actually, it's not that hard at all. CPU is cheap -- it's the bandwidth
which costs, and that isn't really affected until you start
greylisting.
--
dwmw2
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