[Dshield] AOL rejecting emails ?

Tom Laermans tom.laermans at powersource.cx
Mon Jun 30 09:15:22 GMT 2003


What's all the commotion about this dynamic ip blocking..

It's a common technique utilised by many mailservers to reduce spam... And 
indeed a LOT of spam comes through dialups and dsl/cable mailservers.

Blocking these gets rid of a lot of spam, and the obvious open relay 
systems that can be found mostly on cable setups. (There's your port 
blocking discussion again)

AOL and MANY others do this.. they don't do it via reverse dns.. they 
simply have a list of almost all dynamic ip addresses which are used for 
dialup/cable/dsl pools, and they get rejected.

To the original poster: the isp's mailservers is indeed not "rewriting the 
envelope correctly" because as far as I can see you are not using your 
isp's mailserver as a smarthost but are doing direct-to-mx delivery which 
is clearly not appreciated at AOL. (and for good reason)

As for the rfc's some people think they are breaking.. there are none. 
RFC's talk about protocols etc etc, but they are simply denying some mail 
which they think is not appropriate for their network.. which is their good 
right, since it is indeed their network.

Another pooint i saw.. "validity of rDNS" .. what the .. ?
As long as PTR record resolves to A.B.com and A.B.com resolves to the 
original IP what is wrong with the setup? It's not because 
penguin.powersource.cx resolves to 212.239.166.186 that 212.239.166.186 has 
to resolve to penguin.powersource.cx, ya know.. it's fine at 
u212-239-166-186.adsl.pi.be.

Tom




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