Hi Hector,
At 15:59 15-11-2007, Hector Santos wrote:
But I want to make sure I wasn't mis-read. To be clear, the
suggestion really has nothing to do with anti-spam or even
mentioning it. We already have it saving:
4.5.4.1 Sending Strategy
...
The sender MUST delay retrying a particular destination after one
attempt has failed. In general, the retry interval SHOULD be at
least 30 minutes; however, more sophisticated and variable strategies
will be beneficial when the SMTP client can determine the reason for
non-delivery.
This was excellent insight done at the time. Maybe that is enough,
but I do believe a word smith can finesse a new clause or sentence
indicating why a short 2nd attempt may be applicable and highly
desirable for improved outbound mail operations. Maybe something like:
Due to the increase of new SMTP challenge/response receiver
systems, if the SMTP client sees 451 temporary response code
for the RCPT or DATA state, it MAY consider using a shorter
2nd attempt interval, recommended 5-10 minutes. This SHOULD
be for the 2nd attempt only.
The "451" reply code means error in processing. As it's a policy
decision, a "450" reply code is more appropriate.
With the advent of greylisting, a shorter second attempt may seem
desirable to ensure timely delivery of message. However, we should
take into account the impact it will have on the receiver. Such a
short interval conflates the problem for the receiving system if it's
under heavy load. We are also assuming that the greylisting period
will be under five or ten minutes. That may not be the case. For
the proposed strategy to be effective, the sender would have to
determine whether the temporary error was due to greylisting (status
code instead of reply code) and the greylisting delay.
Regards,
-sm