On 28.10.2011 23:17, Steve Atkins wrote:
An ESMTP client, such as your ISP smarthost, will wait a while before
retrying in response to a 4xx deferral. The RFCs say they should wait at
least 30 minutes the first time.
Hence https://datatracker.ietf.org/doc/draft-atkins-smtp-traffic-control/
It's a very lightweight approach that allows a server to tell a
cooperating client how long it would like the client to wait before
retrying.
A related topic is to determine the delivery time based on a message's
priority. As both priority and wait time are about similar topic, perhaps
they shouldn't ignore one another. Priority is being drafted here:
http://tools.ietf.org/html/draft-melnikov-smtp-priority