vvrpgsporcupineorg victor duchovni wed feb 13 2008 100906pm 0700 kevin pendleton wrote victor duchovni wrote specifically isp gives immediate 421 banner ehlohelo negative feedback concurrency overshoot make sticky subsequent blackout time new connections postfix 25 converge isps limits right feedback settings unfortunately comcast follows 4 hour blackout exceed limits rate limits anyway concurrency limits enforced anvil8 example dont way converge right rate limit clear possible design algorithm smtp postfix 25 coverge anvillike connection concurrency limits everything else manual additional caveat convergency towards servers anvillike concurrency limit implemented postfix make small concurrency adjustments delivery limits applicability convergency anvillike concurrency limits scenarios youre sending steady stream email significant amount time otherwise small concurrency adjustments wont much effect wietse tue 05 aug 2008 195731 0500 comcasts 6 recipient per second limit