Here's the patterns we've seen so far:
etc, etc.451 Greylisting enabled, try again in 1 minutes 451 4.7.1 Greylisting in action, please come back in 00:09:00 451 4.7.1 Greylisting in action, please come back later 450 <xxx@xxx.com>: Recipient address rejected: Greylisted for 181 seconds 450 4.7.1 <xxx@xxx.com>: Recipient address rejected: Greylisted for 300 seconds (see http://isg.ee.ethz.ch/tools/postgrey/help/xxxxxx.html) 450 <livejournal.com[204.9.177.18]>: Client host rejected: Policy Rejection- GreyList learning. Please try later. 450 <xxx@xxx.com>: Recipient address rejected: Policy Rejection- Hotkey Greylisting in progress ... Please try again after 2 minutes 451 sender/recip/ip triad greylisted; retry AFTER A DECENT INTERVAL will succeed 450 <xxx@xxx.com>: Recipient address rejected: Greylisting in action. Please try delivery again in 240 seconds. 451 4.3.0 Temporarily greylisted as anti-spam measure. Please try again. 451 <xxx@xxx.com>: Recipient address rejected: Service is greylisted. Waiting for retransmit.
Think I need to write a CPAN module just to return the number of seconds to retry given a string.