North American Network Operators Group

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Re: Outbound mail filtering on large mail / web server farms - justan idea or two that I have

  • From: Michael Loftis
  • Date: Sun Nov 20 13:30:16 2005

--On November 20, 2005 8:48:08 PM +0530 Suresh Ramasubramanian <> wrote:

I originally wrote this lot below as boilerplate for large webhosting
providers that find themselves with several racks full of pizzabox
colos running a web control panel like ensim or cpanel so that the
people actually operating the colos may not have too much clue .. and
these places are typically riddled with lots and lots of exploitable
cgi / php scripts that are broken into and used to send spam using
injection / xss etc holes ..

Some of the ideas here might well apply to what I was talking about in
this thread as well - the two kind of tie in together
I've considered a similar setup. Requiring all mgd servers to always use their local mailers, then at the nearby edge, NATing all outbound SMTP port 25 traffic to a set of mail relays setup to do greylisting, rate limiting, and possibly IDENT checks to make (reasonable more) sure that it's the mail server user talking and not some random software.

Note that I've done none of it...the idea's a bit insane, but, it would definitely make it easier to spot and treat the problems, the only big black eye here is AOL who would probably rate limit the outbound servers quite often, which they already do to our normal mail systems even when things are going well, again, because of forwards. I'd imagine there's a way I could get just the (AOL) forwarded mail pushed to a separate machine with our current (older version) Postfix setup but I haven't actually looked into it. We use SQL based tables for everything in order to make automation much simpler on our end.

I hope this all wasn't too non-operational, it seems relevant to me, so hopefully it's not noise.