Viktor Dukhovni wrote: > Bob Proulx wrote: > > ... http://postmaster.comcast.net/smtp-error-codes.php#RL000001 (in reply > > to MAIL FROM command)) > > Look carefully at the log entry. The "421" is send in response to "MAIL > FROM", not "RCPT TO". So the recipient limit does not look entirely > plausible.
If this was other than Comcast I would accept that immediately at face value but a long history says that Comcast is an unreliable narrator in this story. :-( Also the empirical testing showed that forcing one recipient per message succeeds while three per message was rejected. Interlaced. So while Comcast may be putting sites into buckets and some buckets are allowed to send to three at the same time and others are not knowing what kind of rule is being applied does not help work with it. > A good test would be to disable "pipelining" in a custom > smtp(8) transport, and use that for Comcast. That would definitely > rule out recipient count limits if the reject is still at "MAIL FROM". Sounds like a good thing to test. Will give that a try. > Furthermore, looking at (the reject did say "Please see ..." > > http://postmaster.comcast.net/smtp-error-codes.php#RL000001 > > suggests a reputation issue and rate limits based on that. I don't see > anything about recipient concurrency. Comcast is an unreliable narrator. Same site and same sender can reproduce the problem by sending individually or to three recipients and the messages to three recipients are not accepted. And these messages are not bulk email. My friend is just talking about movies with other friends. > > That it would allow one connection at a time, with one recipient per > > message at a time, and then a small delay between sending of messages. > > The problem is the IP reputation... I agree with you. Because of lack of volume Comcast appears to be rejecting multiple recipients but allowing single recipients. Since single recipients are being accepted okay. But then how do we configure Postfix to do this automatically so that we can gain enough reputation to send more than one recipient at a time? Because Comcast is not rejecting all mail. Comcast is only rejecting mail with multiple recipients. Comcast is accepting mail with single recipients. It's an annoying situation. Will try a test with pipelining disabled. Bob
