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Re: 2821bis consideration - New 2nd attempt Retry Strategy recommendation

2007-11-16 22:30:08

--On Friday, November 16, 2007 9:48 PM -0500 Hector Santos <hsantos(_at_)santronics(_dot_)com> wrote:

Hector Santos wrote:

I probably should of use, 3 days since our original defaults
(non-variable) was once per hour, 72 attempts or 3 days.  And
if you  follow 2821 recommendation, it suggests 4-5 days.
With 30 mins intervals  it yields an awful amount of 240-300

Sorry, bad math - 192-240 attempts!

Except that 2821 suggests rather rapid backoff ("...policy of two
connection attempts in the first hour the message is in the queue, and then backing off to one every two or three hours..."). One could stay with 30 minutes if one wanted to, but the recommendation is more like
   0, 30 minutes, 1 or 2 hours, 2 or 3 hours, 2 or 3 hours,...
My personal experience is that
0, 30 minutes, 30 minutes, 1 hour, 2 hours, 2 hours, 4 hours, and then continuing at four or even six hour intervals yields good results and, at least in the absence of a deliberate delay policy on the server, does not, on average, result in significantly slower delivery than a "try every thirty minutes" plan. That is especially true if the SMTP sender queues are threaded s.t. as soon as a connection can be made to a given SMTP receiver, all pending traffic for that receiver is moved to the front of the queue and transmitted. Of course, any sort of per-message greylisting would foul that procedure up as well.