greylisting and particular MTA mail scheduling

Vernon Schryver
Thu Jan 15 15:57:13 UTC 2004

> From: Aleksander Dzierzanowski 

> my question is about scheduling temporary mail defer by most popular MTA.
> How often and after what time period specified MTA retries delivery
> after 451 temporary error ? And how default defer time (270 seconds) was
> get ?  I'm also interested in all kind of statistics about possible mail
> delays when greylisting is turned into production.

I don't know enough to say much about much of that except the 270
seconds.  I chose 270 seconds or 4.5 minutes as the default embargo
after observing from my logs that many MTAs ignore RFC 2821 and
retransmit after 5 minutes.  I also noticed that while some hit-and-run
spammers retransmitted, few retransmit as long as 4 minutes after their
initial attempt.

Vernon Schryver

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