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2011-10-11 06:58:51


According to my statistic, this year marks a massive growth in SMTP receiver implementing greylisting to the point that some systems are becoming more "elaborate" with their responses, including multi-line response such as this as a response to the DATA EOD response:

451-DEFER - TB3 - Try a lower numbered MX record - S=1  FakeMX - FAKE-MX
451-I=[] X=tarbaby []
451-HELO=[] F=[xxx(_at_)xxxx(_dot_)com]
451 T=[user(_at_)xxxxxx(_dot_)com]

More so, the delays requires to retry vary greatly and sometimes it seems like it can a day.

I think we finally need an official IETF "BCP" written up to begin maybe coordinate the client/server operation to help to alleviate the increasing delays and wasted retries to the point where i am now hearing complaints with the ATTEMPTS are exhausted and the destination is "flagged" as bad domain or address.

One suggestion for the GREYLIST "BCP" is if a receiver is going to block for an extensive time, it should maybe provide that feedback in should official response format.

For use, our stock retry attempt table has initial 5, 10, 15, 30 minutes delays before it fall backs to 1 hour for the remaining attempts up to 4 days.

Greylisting has become essentially a "pseudo" standard today and too many systems are becoming too aggressive with delays. This needs to be coordinated better.

I think someone should take up the effort to begin/draft an GreyList BCP for systems to follow.