> Postscript: I do notice that 67.91.139.138 reverses to > <ip67-91-139-138.z139-91-67.customer.algx.net.>. I've heard rumor > that some spam filters will consider suspicious any IP address with a > reverse DNS that "looks like that".
This is much more than rumor. In addition to regex style filters that look for generic/dynamic looking PTRs, more and more sites are also blocking if the PTR does not match the A. Put it this way, if your relay's PTR does not match its A record it *will* experience delivery issues. This will only get worse so it should be addressed now rather than later. Fixing this is not as big of a problem as it was a couple years back if you have a business level account. Here in the U.S., even AT&T dsl customers can now get their reverse DNS delegated or changed. There are a few 3rd party dns providers around that will host reverse dns zones (I can't recommend easyDNS enough for their great support). Email admins should also be aware of the Spamhaus PBL list which is included in the heavily used zen.spamhaus.org blacklist. You can sign up and authorize the specific nodes in your IP range that relay mail. The PBL attempts to list swaths of the Internet that are used primarily by dynamic or "end-user" type nodes that shouldn't be sending mail. See: <http://www.spamhaus.org/pbl/index.lasso> If these Reverse DNS or Dynamic IP range type issues cannot be addressed, the only other option is to setup your system to relay through a "smarthost" that is in correctly configured IP space. This would typically be the upstream ISPs mail relay. In Exchange 2003 this is configured in properties of the default smtp virtual server->Delivery tab->Advanced...->Smart Host field ~JasonG -- ~ Ninja Email Security with Cloudmark Spam Engine Gets Image Spam ~ ~ http://www.sunbeltsoftware.com/Ninja ~
