On 2025-08-24 at 19:39 +0100, Simplelists - Andy Beverley wrote: > I've just checked now and interestingly the deliveries to the same > Gmail > server immediately before and immediately after succeeded. If it had > been an actual DNS error I would have expected more than one failure > because of caching (although who knows what's the other side of that > single IP address)
Not necessarily. I expect there is a dns caching server which is returning a failure due to timeout, when it goes up the gmail stack, it somehow gets converted into an empty list, not remembering that there was an error (or perhaps they do that willfully, because they don't want to 400 missing rptr which don't return anything?) But on the next email, the delayed got into the cache, so it's now served immediately. It may even happen that the timeout happens at the higher-level code that queries the DNS stack, not inside the DNS resolver. > > Had the relevant DNS queries resulted in timeouts or other > > transient lookup problems, and the remote MTA were Postfix, the > > reject code would have been a 4XX. I don't know that Gmail gets > > this right, but I'd be surprised if they got it wrong, that'd be a > > serious bug, worth contacting their engineering team about. > > Anyone have a contact...? > > Many thanks, > > Andy Brandon is in the mailing list, he sometimes filled the needed internal google tickets. _______________________________________________ mailop mailing list [email protected] https://list.mailop.org/listinfo/mailop
