Uncle George wrote:
I'm not sure that's the case. It just means the those who use qmail
AND (have bad reverse lookup OR are on a dynamic IP address) will not
be able to send email to my domains UNLESS I whitelist their host.
I guess i'm at a loss here. Exactly how would trying each MX record in
turn prevent your filtering techniques from processing reverse
lookups, or dynamic ip's.
but the guy is correct. qmail is owned by one person, and is not
likely to change. The followers of qmail, I think, would have
adopted such a MX strategy, if it was *exactly* spec'd that way into
one of their mandatory patches.
I process about 4 million messages a day. As you know graylisting is a
popular spam fighting technique and gets rid of spam using 4xx errors
and counts on the fact that spam zombies don't retry. But greylisting
has its drawbacks like delaying good email. So I don't use it.
What I do instead is sort of selective graylisting targeting dynamic IPs
and bad RDNS. But instead of delaying them for a long time with
graylisting I only use the tem error on the lowest IP and accept it on
the next highest IP. And this works for all MTAs except qmail that will
keep trying the lowest MX till it times out.
But - it only happens to qmail users with dynamic IPs or bad RDNS. And I
can add IPs to a braiddead hosts list to bypass it if someone complains.
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