AOL blocking DynDNS Mailhop-Outbound

[Tom Metro]

Rich Braun wrote:
> ...the evidence more likely points to [AOL's] filtering software 
> looking beyond the relay server to examine headers (such as Received
> or X-Originating-IP) to find other reasons to reject a message. My
> own IP address appears at least twice in the first few lines of headers.
> 
> What I /wish/ DynDNS would do is strip such IP addresses from
> outbound headers (they aren't put there by Postfix on my end) and
> replace them with a customer-ID string.

So your theory is that AOL is examining Received headers and rejecting
your messages based on what it finds. What specifically would it be
looking for?

Consider that the vast majority of ISPs have customers using dynamic IP
ranges connecting to a mail relay. These dynamic IP addresses almost
always appear in some of the headers.

How is DynDNS's MailHop different?

If the entire message is being subjected to Bayesian filtering, it isn't
inconceivable that subtle differences could trigger a spam threshold.
Perhaps with other ISPs the filter becomes accustomed to what netblocks
the embedded IP addresses come from, yet with MailHop they're all over
the map? But this seems unlikely.


> AOL's rejection code is cited as 554 RLY:B1... "This error message is a
> dynamic block on our system. Dynamic blocks are placed on an IP address when
> the IP's statistics break our threshold. These are automated blocks that are
> removed by the system within 24 hours once the complaints are again below the
> threshold."
> 
> Maybe MailHop's address 205.188.146.194 is the target of AOL's filter...

That seems far more likely. Have you discussed this with DynDNS? Perhaps
they have customers (or hacked customer accounts) that are abusing the
relay. Maybe they need to put better abuse controls in place.

I also wonder if AOL has different profiles for different types of
senders. For example, the statistical profile of a corporate mail relay
is going to be quite different from that of an ISP's relay from AOL's
perspective. Maybe they have the MailHop server misclassified? (Or there
is something else about MailHop that is hampering AOL's filter from
establishing a valid baseline.)

 -Tom

-- 
Tom Metro
Venture Logic, Newton, MA, USA
"Enterprise solutions through open source."
Professional Profile: http://tmetro.venturelogic.com/