On 1/7/18 6:30 PM, Stephen Satchell wrote:
On 01/07/2018 03:09 PM, D'Arcy Cain wrote:
On 01/07/2018 01:15 PM, Yuval Levy wrote:
would detract from the main issue which is "silently discarded emails,"
I behavior that in my view is plain wrong and threatens the usefulness
of email more than a few false positive spam messages.
Absolutely. There are only two things that an MTA should do with email,
deliver it or bounce it. Silently dropping is plain wrong.
But the best time to bounce the mail is during initial delivery.
Microsoft makes it clear that their Smart-whatever is done *after* the
SMTP server has accepted the mail. Rejecting the mail afterwards has
the risk of sending the bounce not to the sender, but to another party
whose name just happened to be in the From: field.
Most of the spam I've received over the years doesn't have a live
account as specified in the From: field. So the problem is, where to
send the bounce notification if you already said "I got it"?
You guessed: you don't. You drop the mail, and that's that. No
side-channel spaming.
When I smart-hosted a bunch of Plesk and CPanel systems with edge
PostFix servers, I had to be very careful not to run into this very
same situation with quotas. It was tedious and complicated and ugly,
but I made it work. I also had those same servers accept mail from
the Web boxes and did anti-spam, dropping "bad" e-mails after sending
a note to my admin logs about the dirty delivery.
(I was able to find the small number of spammers in a community of
thousands of accounts this way, and closed them due to violations of
the terms of service.)
Which is why a QUALITY MTA will do all the test that decide IF a message
will be delivered before accepting the message. Test for where to
deliver (normal inbox/spam box) can be done later. This means you need
to validate recipient & quotas etc before acceptance. If quota tests
fall behind and an over quote message gets accepted, you still should
deliver and consider the quota limit 'soft'.
Of course, the issue now becomes that most of the 'free email' systems
aren't quality system, so the above promise isn't kept, and some stuff
is just dropped.
--
Richard Damon
