Hello, we're facing the following problem: postfix is configured to verify recipient addresses. The backend servers are mostly Exchange in various versions. Many of them use tarpitting. We guess that are default values. The address probe sent by postfix receive a result after 5 seconds delay. reason: tarpitting. Meanwhile postfix accept the message and we generate bounces later :-/ The next message to a - now known undeliverable - address is directly rejected by postfix. That's expected.
Does the parameter address_verify_poll_count and address_verify_poll_delay control these timings? Looking at the defaults it matches perfect to the volume of affected messages here. Am I right to interpret address_verify_poll_count=3 + address_verify_poll_delay=1 (under stress) is to short for 5 seconds tarpitting? If so, what are the suggested changes? I would try address_verify_poll_delay=2 first. 3x2 seconds = 6s > 5s tarpitting Opinions? Andreas
