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Re: I-D SMTP Extension for Greylisting

2011-10-24 09:48:26

I have started on -01 draft.

- XML corrections so that the XML2RFC TXT conversion (some figures, list, line spacing) is laid out correctly.

- Added text to background section paragraph highlighting the fact the proposed SMTP extension does not change RFC5321 due to the fact Greylisting and MTA specific retry strategies are already out of scope.

- Added to section 3.1 SMTP Client/Server Implementation SHOULD|MAY|MUST [NOT] semantics. This will need review to get right.

- A consideration to simplify Servers implementation of the retry=time tag where the server blocking time is already known in seconds and would be an easier text response change is replace the text word to "retry=seconds" compared to calculated the time in a HH:MM:SS format.

If considered, I think the ABNF change would be:

   retrytime   = ("retry=" [days "-"] hours ":" minutes ":" seconds) /
                 ("retry=" totalsecs)

   days        = 2DIGIT   ; 00-99
   hours       = 2DIGIT   ; 00-23
   minutes     = 2DIGIT   ; 00-59
   seconds     = 2DIGIT   ; 00-59
   totalsecs   = 1*(%d48-57) ; total seconds to delay

If this suggestion for a 2nd syntax format is acceptable, is the ABNF correct?

Hector wrote:


An SMTP Extension I-D was posted

    Title           : SMTP Service Extension for Greylisting Operations
    Author(s)       : Hector Santos
                          Evan Harris
    Filename        : draft-santos-smtpgrey-00.txt
    Pages           : 17
    Date            : 2011-10-23

   GREYLIST is a SMTP extension to formalize the widely supported
   Greylisting mail filtering method and to help support SMTP rejected
   transports by following a new formal structured 4yz server temporary
   rejection response by including a retry=time tag string which SMTP
   clients can use to optimize the rescheduling of the mail delivery
   attempts.  With adoption, network overhead reduction in wasteful mail
   delivery attempts will be realized.


I would like to thank all the people who provided guidance in producing this initial draft. Much obliged. It is far from done so all input and considerations from large, small to mom and pop people would be greatly welcome.

Our mail servers have already implemented the SMTP extension so if you need a test site, you can send mail to:


If I have written to you in the past privately, you are probably already auto white listed. So use an different sender account if you are interested in testing the server with its 45x greylist responses that now include the proposed retry=time hint information.

In addition, if you are exploring the proposal for your own Greylist server implementation, provide the address info so we can run test as well.