Thanks. Even with TLS, the destination port (either 25 or 365) is well-known, right, as is the source IP? At the minimum RBLs could be used for that encrypted traffic. Frank -----Original Message----- From: Joel Jaeggli [mailto:joelja@bogus.com] Sent: Monday, June 23, 2008 2:20 PM To: frnkblk@iname.com Cc: nanog@merit.edu Subject: Re: Cloud service [was: RE: EC2 and GAE means end of ip address reputation industry? (Re: Intrustion attempts from Amazon EC2 IPs)] <snip> dpi boxes from a number of vendors can do that sort of thing... whether they can do it fast enough to be inline with your compute cloud is another question entirely. That said the result is fairly perilous when rejecting a message involves forging packets. and of course tls supporting mta's will be opaque to the network traffic inspecting device.