Hi all,
Whilst doing some testing and research on Exchange2007 for a paper I came across a "feature" in Exch2007 called Sender Reputation.
By default each Microsoft Exchange 2007 Edge Transport will (on receiving mail from an unauthenticated connection):
"Perform an open proxy test when determining sender confidence level".
The description given for this is:
An open proxy test tries to connect to the sender originating IP address with an SMTP request. If the Microsoft Exchange Edge Transport server receives an SMTP request through known open proxy ports and protocols, the sender is considered an open proxy and potential threat, and the sender reputation level is adjusted accordingly.
I have no intention whatsoever of using Exch2007 but I can't make up my mind if this is a useful method, or just trouble brewing. I understand that this is not specifically Exim related but could have a some knock on effects/implications for anyone running Exim (if every message sent to an exchange box tries to generates a new connection back). I'd be interested in the lists opinions on the following:
1) Is this useful/workable or just a Pain In The Ass for everyone else?
2) How will this effect Exim if at all (Lots of extra unnecessary/dropped connections at Exim or the firewall or anything more serious)
Aside: MS claim to have patented this technology (see below)
Sender reputation uses patented Microsoft technology to calculate the trustworthiness of unknown senders. Sender reputation gathers analytical data from Simple Mail Transfer Protocol (SMTP) sessions, message content, Sender ID verification, and general sender behavior and creates a history of sender characteristics. Sender reputation uses this knowledge to determine whether a sender should be temporarily added to the Blocked Senders list. For more information, see Sender Reputation.
http://technet.microsoft.com/en-us/library/bb124512.aspx
Sorry for the long post, I just thought this be worth mentioning to other users on the list especially as more Exch2007 servers start to appear on the net.
Thanks
Jason_Meers
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