Dnia 28.02.2023 o godz. 11:10:05 Julian Bradfield via mailop pisze: > On 2023-02-28, Jaroslaw Rafa via mailop <mailop@mailop.org> wrote: > > Another nonsense thing for me is that some senders - again, mostly the big > > ones - retry almost *immediately* (often from a different IP address) if > > they encounter a 4xx, and after a few such unsuccessful retries (within only > > a few minutes) they eventually give up. I wonder what had in mind someone > > who designed it that way? In a very broad sense, 4xx means some transient > > problem on the receiving side that will eventually get fixed, and then the > > mail will be accepted. But fixing any problem requires time. Did someone > > who designed this behavior expect that the problem will "miraculously" > > disappear if they retry immediately a few times? > > Maybe worth pointing that people do greylisting, and with > greylisting it's helpful to retry quite soon. Immediately isn't > useful, but within five minutes is. (I personally have one-minute > greylisting set.)
I do greylisting, and that's how I found out about the immediate retries. I run postgrey with default setting which is 5 minutes, and I often see in logs multiple retries within those 5 minutes, with first ones being really almost immediate (15-30 seconds). I have no other MXes, so I can't observe retries to other MXes, but I often see retries FROM different IP address than the original attempt, which count as new entries for greylisting, as greylisting works on triplet (client IP address, sender, recipient). And so they often try, say, 5 different IP addresses within 5 minutes, all tempfailed of course (because from greylisting point of view each one is a completely new delivery attempt because of different IPs), and then retry only after a hour or so (when the mail gets finally delivered) - but sometimes don't retry at all... Postgrey by default whitelists several senders known to behave this way, but not all... -- Regards, Jaroslaw Rafa r...@rafa.eu.org -- "In a million years, when kids go to school, they're gonna know: once there was a Hushpuppy, and she lived with her daddy in the Bathtub." _______________________________________________ mailop mailing list mailop@mailop.org https://list.mailop.org/listinfo/mailop
