>Mail admins wanting matching forward/reverse DNS and hostnames that >don't "look dynamically generated" is probably more of a human than an >RFC thing:
Right. Spam filtering depends on heuristics. Mail from hosts without matching forward/reverse DNS is overwhelmingly bot spam, so checking for it is a very effective heuristic. Mail from hosts with names that look dynamic is also quite spammy, but figuring out what looks dynamic is quite hard. I know someone who's been tuning his regexes for years. For most people, third party lists like the Spamhaus PBL are more reliable. R's, John
