On 2015-05-28, Kevin Chadwick <m8il1i...@gmail.com> wrote: > On Mon, 18 May 2015 17:39:11 +0100 > Craig Skinner wrote: > >> RFC 5321, in section "4.5.4.1. Sending Strategy" has: >> >> .... >> ... >> .. >> >> 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. ..... >> >> >> > Are there any experiences, after how many hours/days the sender >> > side (at the large ones like google, yahoo, hotmail, etc) >> > gives up? >> > >> >> I didn't make notes on that, sorry. >> >> From memory, they honour the 4 day rule. > > I believe so with the possible exception of hotmail as I seem to > remember thinking it was typical that microsoft were ignorant of the > RFC's and stopped trying after hours.
If it was a rule it would be 'MUST'; in this case it isn't even 'SHOULD' rather just a general recommendation (4 days gives chance for a fault occurring Friday evening to be fixed after a long weekend without bouncing). For some types of email, if it isn't received fairly promptly, it's too late so there is little point in retrying it, so senders act accordingly.
