Aside from the possibility that the message is simply wrong, or the implementation broken, is your mail server acting like most other servers when presented with a failure (soft or hard)?
Your posting seems to be that you give up after the second try. Most servers will try at least 5 times for such, only giving up after hours (sendmail defaults at 4 days). In fact, if you're giving up in a unusually low number of retries (like just one), that may cause your IP to be penalized in some way - increasing retries you need to do OR outright blacklisting - but getting a 4xx simply because the code handling greylisting only answers in one way, and the permanently blocked by the greylisting code gets the same answer as greglisting proceeding as intended. On 2021-04-20 05:06, Neil Youngman via mailop wrote: > I have observed that messages from our system are temporarily rejected > as greylisted by one destination but they are never accepted on retry. > The response is logged as "DATA: 451 0.0.0 1 recipients being greylisted > for 5 minutes". We retry after 10 minutes and get the same response. > > Normally I would expect the retries to pass greylisting. Does anyone have > any insight into why this is not behaving as expected? The destination is > exeter.ac.uk. > > Neil Youngman > > > _______________________________________________ > mailop mailing list > mailop@mailop.org > https://list.mailop.org/listinfo/mailop > _______________________________________________ mailop mailing list mailop@mailop.org https://list.mailop.org/listinfo/mailop
