On Wed, 30 Aug 2006, Frank Ellermann wrote:
they seem to be oblivious to the fact that spammers are
using their spamtrap addresses for MAIL FROM! Should I
waste my time trying to explain why their system needs
some work?
AFAIK they know this. I wonder why you send unsolicited
DSNs to unverified Return-Paths. That's net abuse, or did
I miss something in your scenario ?
My client is getting blacklisted on average once every 18 days.
That is not very many bogus bounces. A blacklist lasts for 24 hours, so
it is not as bad as I thought originally. Of course, I immediately reject
all the obvious forgeries (HELO fail, for instance - amazing how many
fogeries use my own HELO). SPF FAIL gets a reject. If there is
a valid PTR, or it gets a PASS, or a guessed pass from "v=spf1 a/24 mx/24 ptr",
or has a valid HELO, it gets delivered (and content filtered). There is
a DSN for quarantined mail - but only if MAIL FROM gets SPF or guessed PASS
(I think - I'll double check the code).
There are two circumstances in which I send a DSN by default:
a) SPF softfail - because the sender is asking for debugging help
b) SPF NONE, no PTR, invalid HELO, no guessed pass (3 strikes) - there are a
LOT of otherwise legitimate senders with this braindead setup. It causes a
lot of problems to simply reject them because they are clueless (or
they would have done it right) and don't know what to do.
Whether to send DSN is configurable. I simply reject case b in my own setup.
But clients are concerned about missing email from email-clueless customers.
Spamcop suggests using another public IP for DSNs. This is reasonable
and feasible for most of my clients.
I have to walk a fine line between demanding authentication as much as
possible, and not blocking clueless senders. Eventually those clueless
senders need to get a clue.
--
Stuart D. Gathman <stuart(_at_)bmsi(_dot_)com>
Business Management Systems Inc. Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flammis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.
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