victor duchovni dxdewmdieulnutmorganstanleycom 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 viktor disclaimer offlist followups get onlist replies get ignored please ignore replyto header unsubscribe postfixusers list visit httpwwwpostfixorglistshtml click link response solves problem best way thank send worked thanks followup must respond please put worked thanks subject delete quickly tue 05 aug 2008 195047 0500 comcasts 6 recipient per second limit