Am 07.10.2023 um 22:41:01 Uhr schrieb Kirill Miazine via mailop: > Recently I experienced a very "interesting" case which gave my > personal email server "poor" "sender score" due to high rate of > emails sent from my server to non-existent users.
Normal, because spammers often have mass of non-existing (mostly not anymore) addresses and because these lists are often sold, many spammers will try it. > I think I figured out what it was. A user sent an email to another > family member, but using contact's old email domain which used to be > hosted by Fastmail, but where no such user would exist anymore (I > don't know if domain still exists as a domain at Fastmail, but > clearly MX point to them). > I'd guess a 5xx response would be appropriate -- at least on port 25, > but Fastmail sent 451, and made my Exim try -- and keep re-trying -- > all IP addresses of all their MX. I have very conservative retry > rules, so emails would be kept in the queue for a month... That is fastmails bad configuration. Permanent errors like "mailbox doesn't exist" must have a permanent error code (5xx) to avoid retry. > Senders to Fastmail beware, and maybe consider treating their 4xx > errors as permanent. Fastmail must fix that - every MTA will try it again and again if a 4xx error occurs and that will flood them with the messages many times. _______________________________________________ mailop mailing list [email protected] https://list.mailop.org/listinfo/mailop
