While I don't doubt this, I often see from DIY types some really lazy smtp habits. If they don't have their reverse DNS matching the forward DNS as well as the HELO name matching that as well, then, yes, that will be a major red flag for anti-spam systems. Reverse DNS is pretty important and weighed heavily.
smtp delivery is something of a black art, but at the very least those things need to be set correctly. Its also worth mentioning that if you have 'spammy' applications that opt people in to mailings then a lot of people just get pissed off and click the 'junk' button over and over instead of unsubscribing properly. So think twice before auto-subing customers or enabling 'mail me replies' by default on forums and such.
I also learned the hard way that once you're on Cisco Ironport's spam list, then you really can't get off. There's no one to talk to. Its supposed to be automated. In practice, that means months before your domain is unblocked. I find most Ironport admins just use that sole list even while Cisco recommends they use many and weigh the average. After a stupid config change that opened our smtp to relaying, we got off everyone's blacklist but IronPort. IronPort is pretty much the defacto standard in several types of enterprise. My fix? Get a different IP address for the mail server.
smtp delivery is something of a black art, but at the very least those things need to be set correctly. Its also worth mentioning that if you have 'spammy' applications that opt people in to mailings then a lot of people just get pissed off and click the 'junk' button over and over instead of unsubscribing properly. So think twice before auto-subing customers or enabling 'mail me replies' by default on forums and such.
I also learned the hard way that once you're on Cisco Ironport's spam list, then you really can't get off. There's no one to talk to. Its supposed to be automated. In practice, that means months before your domain is unblocked. I find most Ironport admins just use that sole list even while Cisco recommends they use many and weigh the average. After a stupid config change that opened our smtp to relaying, we got off everyone's blacklist but IronPort. IronPort is pretty much the defacto standard in several types of enterprise. My fix? Get a different IP address for the mail server.