To elaborate: I have two spam filters in front of SM. Together they are adequate, but both have idiosyncrasies that make me want something better. Going through the capabilities of SM 17, I was impressed by what is included, and began thinking that an SM Gateway configuration might be better than either of them. Unfortunately, Reverse DNS filtering is a deal killer for me. If I get spam from "server7.malware4u;com", I want to block all of their servers, not just the one that sent that message, so i need a block rule like "ends with malware4u.com". We also use Reverse DNS for country blocking, such as "ends with .ru". We have very little need for international correspondence, so we block a long list of country codes. Reverse DNS can be fraudulent, but it is usually accurate and useful, and it blocks a lot of our incoming mail.
I have been reviewing the market offerings, and have been shocked and baffled by the number of products that offer IP Filtering without Reverse DNS filtering, or Reverse DNS filtering without IP filtering.
A good spam filter also needs a good message review capability, so the admin can decide which allowed messages should be blocked, which blocked messages should be allowed, and which rules should be changed to achieve the desired result. SmarterMail has no log review for the administrator, and I don't think a sufficient log review tool can be constructed even if all of the relevant log files are in detail mode and optimally parsed.