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Re: Time to check the rate limits on your mail servers

  • From: Suresh Ramasubramanian
  • Date: Thu Feb 03 07:13:18 2005
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On Thu, 3 Feb 2005 11:42:55 +0000, [email protected]
<[email protected]> wrote:
> that botnets are now routing their mail traffic through the local
> ISP's mail servers rather than trying their own port 25
> connections.

Now?  We (and AOL, and some other large networks) have been seeing
this thing go on since over a year.

> Do you let your customers send an unlimited number of
> emails per day? Per hour? Per minute? If so, then why?

Doing that - especially now when this article has hit the popular
press and there's going to be lots more people doing the same thing -
is going to be equivalent of hanging out a "block my email" sign.

One additional thing that I think wasnt mentioned in the article -
Make sure your MXs (inbound servers) are separate from your outbound
machines, and that the MX servers dont relay email for your dynamic IP
netblock. Some other trojans do stuff like getting the ppp domain name
/ rDNS name of the assigned IP etc and then "nslookup -q=mx", then set itself up so that all its payloads get delivered
out of the domain's MX servers

Suresh Ramasubramanian ([email protected])