>> The legitimate mail that passes through my mail server comes from >> hosts / networks I might not hear from again for months, by which >> time I have to potentially wait 24 hours for the greylisting / mail >> server to try again.
I run greylisting on an email server with several thousand email accounts and think its great. Reduced system load drastically. I also have a perl script I have wrote that runs every minute and looks at all messages that arrived in last 60 seconds and if spamassassin gave them a score of less then 5 it adds the sending MTA to a whitelist. It also removes any from the whitelist that have sent a message that scored over 5. The whitelist goes back 6 months and is continually refreshed by the script. The whitelist typically has 40K IP's in it. As a result no one even notices the greylisting, AFAIK...
