Has AOL become the Police of the Net?
No, but as with any of us, they are the police of their own MXs, and you can imagine the scale and expense of their spam problem, with 20+ million targets.
Blocking all DUL subnets is crudely effective, but, from what I see, almost no mail from direct DUL subnets to MXs is legit, so crudeness pays.
What's nice is that many operators are now naming their PTR hostnames so they are easily identifiable, and distinguishable, from their MXs and outbound relays, so you can block MTAs easily by domain of PTR hostname:
client.attbi.net ipt.aol.com ptr.us.xo.net ( aka egregious spam farm ) client.mchsi.com client.insightBB.com dsl.telesp.net.br user.veloxzone.com.br customer.telesp.net.br
Others are not so convenient since the tell-tale label is not at the 3rd label:
dsl-200-78-1-233.prodigy.net.mx
But you can block their MTA by PTR hostname with regex:
/[dsl|cable|pool|docsis|etc|dhcp|dial|etc](.*)\.(.*)\./
and then handle the minuscule number of false positives.
If you are on a fixed DUL IP (paying extra $), then try to get your IP provider to give your outbound relay a different PTR hostname to escape the above PTR blocking scheme.
Len
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