One nice thing about the new postfix is that the error messages are much more explicit. The old version used to say “unknown host” if the inverse DNS was missing, if the forward DNS pointed to a different IP address, or if the EHLO command was wrong. The new one says things like, “EHLO must be a fully qualified domain name”, etc, spells it out much better. Hopefully this will translate into having to spend less time helping clueless system administrators configure their mail servers.
The gray listing has substantially reduced the amount of spam getting through. Not zero percent but about 5% of what made it through previously and most of that gets snagged by spamassassin.
The Bayesian filters still need your help to train them recognize spam. Spam should be “bounced” (not forwarded) to “firstname.lastname@example.org”. You can do this with pine or any other mailer that has a bounce function. The bounce keeps the original originating address where forwarding changes the originating address to your address in many mailers.