AOL rejecting mail from IP's w/o reverse DNS ?

Suresh Ramasubramanian suresh at
Wed Dec 3 17:24:24 UTC 2003

Greg Maxwell  writes on 12/3/2003 11:39 AM:

> Seriously, do we really need SMTP peering agreements?  I don't know of too
> many places that are UUCPing their email... SMTP traffic already crosses
> (BGP) peering agreement controlled links. If putting contractional
> obligations there fails to work why should we believe some new and less
> understood system would be any more effective?

What about speaking plain old smtp, but with transport / mailertable 
rules routing all  mail for domain X (say AOL or MSN) to "special 
access" servers that have firewall ACLs allowing only connections from a 
restricted set of IPs?

So AOL talks to (say) us and says "hey, instead of  mail from our users 
waiting like all other  mail to connect to port 25 on your MXs, set 
aside a cluster of MXs that'll permit smtp connections from [this /24]"

We then take these emails and deliver them as usual.  Just that AOL mail 
to our users gets delivered faster, doesn't clutter our MXs ... and we 
can send mail to AOL over a similar back channel.

As a bonus, monitoring and controlling spam on these would be far easier.

Yes it won't scale.  But it is not intended to scale - it is just 
intended to be a series of agreements between large providers that will -

* reduce congestion / endless mail queues on regular MXs / outbound 

* let inbound / outbound flowing through that back channel get more 
easily managed [and monitored for spam] than if it were to take the 
usual route.

Think of it as taking a short cut through a toll road instead of the 
usual toll free traffic jammed highway.


srs (postmaster|suresh) // gpg : EDEDEFB9
manager, security and antispam operations

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