Hello, On Fri, Jun 23, 2023 at 11:13:56PM -0500, Al Iverson via mailop wrote: > What if we just got to the heart of the matter and admitted that > greylisting is useless 2023?
For me that isn't the heart of the matter. I mean it's an interesting discussion still, but what surprised me about this discussion is how easy it is to unwittingly hit one of SendGrid's heuristics here. In the specific case at hand it seems that the OP is greylisting SendGrid for being on some sort of blocklist, and the specific mention of "blacklist" in the 4xx response is hitting a SendGrid heuristic that says "don't bother to retry these", so messages are actually being lost. I think it has implications beyond greylisting. When it comes down to SMTP responses I used to be more on the side of including verbose text as to reasoning rather than just a terse code or a generic message. This turn of events is pushing me towards the "terse code" stance because I don't want to unwittingly have my 4xx be interpreted in other ways. I'm talking about 4xx that have nothing to do with greylisting here. I wouldn't go as far as to characterise my belief that 4xx should always be retried to be as firm as fanaticism or religion. Like I say, I can see why in some specific cases large senders might not want to. The combination of seeing 4xx and "blacklist" being enough though seems like a pretty blunt tool. I'm surprised at that. I don't have an appreciation of the scale but are the rewards on SendGrid's side really worth the risk? I think if I was doing it I'd want to be more specific and maybe even try to also match on recipient domain and/or MX IP or ASN or something. It strikes me that if there is an actual problem with messages staying in a queue for days because of perpetual 4xx it's going to be with large mailbox providers not every enthusiast with a Linux box and a handful of users. Cheers, Andy -- https://bitfolk.com/ -- No-nonsense VPS hosting _______________________________________________ mailop mailing list mailop@mailop.org https://list.mailop.org/listinfo/mailop
