On 10/25/2010 9:38 PM, utahnix wrote:
Hello all,
This question has probably been asked on this list before, but
maybe not quite with these circumstances. I'm hoping one of
you can give me some direction.
I've got a fairly typical Postfix setup... Postfix, Cyrus
IMAP, ClamAV, SpamAssassin... all on Linux.
Anyway, I've set up greylisting with Postgrey to help cut down
on the junk mail that I get. I've set it up with default
values (deferral of 300 seconds, etc). Well all seems good and
fair except some of my regular senders can't seem to get their
email through. I've checked my server logs and I don't even
see their email address mentioned (it doesn't appear to even
reach my machine). Several of the emails in question are Yahoo
or Gmail. What's odd is that I have both a Yahoo account and a
Gmail account, and I can send myself mail with no problems.
"Well known" mail servers shouldn't be subjected to
greylisting; it unnecessarily delays mail that will always
pass later.
I disabled Postgrey temporarily and had these senders re-send
test messages from their addresses, and it worked (I got their
messages). So something was certainly hanging things up. I
just wish I knew what that was.
If postgrey and/or postfix didn't log deferring their mail,
then the problem was elsewhere.
This got me thinking... my ISP requires that I forward all
outbound email through their SMTP server. Because their mail
server (the SMTP relay I'm required to relay mail to) has
suddenly been added to various RBLs for repeated "deferrals",
is it possible that my greylisting is what is getting them on
those RBLs?
I've never heard of a server being blacklisted for deferrals.
That's crazy talk.
At any rate, they wouldn't be blacklisted for your greylisting.
If you're sending tons of non-delivery notices out through
your ISP, that's another matter. That could get them
blacklisted as a backscatterer, and if they're paying
attention, your service disconnected.
The Postgrey does cut down on the spam significantly,
particularly when used in conjunction with SpamAssassin and
RBLs like SpamCop and SpamHaus. I'd like to keep Postgrey if I
can, assuming that my delivery problems are not directly
associated with Postgrey... but if my circumstances with my
ISP won't allow me to greylist, then disabling Postgrey might
save me a headache.
I guess I'm looking for some advice as to whether Postgrey
could cause problems with my ISP (they run Exim on FreeBSD and
firewall outgoing tcp port 25 everywhere but on their one mail
server) but I don't know much more than that), or if there are
some settings I should change to improve my greylisting setup.
You have no evidence that postgrey is the problem. With the
evidence you do have -- nothing in the logs -- it seems quite
unlikely postgrey is the problem.
And just to clarify, port 25 is only blocked on the outbound.
Inbound email comes straight to my mail system, which is only
composed of one machine.
Advice is very appreciated!
You need to look further. Make sure you're not a backscatter
source; don't accept mail you can't deliver to the intended
recipient. It's pretty common for servers to be blacklisted
as a backscatterer.
-- Noel Jones
