[Dshield] DNS MX and SPAM again

Robert Dodd bobdodd at sheperd.com
Tue Sep 16 02:20:32 GMT 2003

Please consider the following. The domain that I manage has two properly
configured MX records which are routed through our firewall to an anti-spam
appliance. Here's the problem, our firewall is rejecting attempts to connect
on port 25 of our domain's A record at the rate of ten per second. Do some
mail servers try the "A" record even when "MX" records are available? Or is
this another symptom of spam gone wild?

Our DNS records are hosted by our "major" ISP (not this one, I'm at home).
We have recently changed ISPs and completely regenerated our DNS records.

To restate the problem in extreme shorthand:
A .100
MX .104 preference 10
MX .103 preference 20

Why are connections attempted on port 25 of .100 ?

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