Ask HN: Yahoo disregarding RFC 5321 retries
by beezle on Hacker News.
Had a firewall issue that temporarily affected port 25 but was not identified for just over 24 hours. In the process of resolving, a test message was sent from a yahoo account to the domain in question. Yahoo sent an ‘unable to deliver message after multiple retries, giving up’ message after exactly three hours. Three hours is exceedingly short and my understanding has always been that mail is re-tried for a number of days with a backoff algorithm controlling how often. Is this now common? I am left to wonder how much mail was lost for good during this outage because others have also taken the Yahoo approach. RFC 5321 suggests: Retries continue until the message is transmitted or the sender gives up; the give-up time generally needs to be at least 4-5 days. It MAY be appropriate to set a shorter maximum number of retries for non-delivery notifications and equivalent error messages than for standard messages. The parameters to the retry algorithm MUST be configurable.