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Re: SMTP traffic control (was Re: We need an IETF BCP for GREY LISTING

2011-10-13 12:20:32

Steve Atkins wrote:

On Oct 13, 2011, at 7:51 AM, John Levine wrote:

So, if the server says 'retry in 1 hour', and the client retries every 5 minutes, that's no crisis, just a wasted bit of effort for the client and the server. ....
Since the number of MTAs vastly exceeds the number of greylisters,
don't you think it would be better for greylisters to work with the
existing retry schedules that MTAs use than to try to persuade a
million MTAs to implement a new feature that is of at best marginal
use to them?

We're not talking about greylisting, and haven't been for quite a few levels of this thread. We're talking about use of 4xx deferrals
for traffic management and prioritization.

However, the blur includes both and and I would suggest it be valid in a related BCP it will include current considerations for how clients have been designed to behave and follow SMTP retry recommendations.

Ultimately, a "retry=hint" suggestion would apply to both concepts.

I think that in most cases, traffic control is done with 421 at the connection level, and traditionally GL is done at either RCTP or DATA. But now you do see it at connections too - based on the varied text response of what I see out there, like

    421 too many connections
    421 temporary rejection - try again later

Who knows if the latter is just another way of limiting loads, but if a GL concept, it only based on IP only which IMO, it not a true GL concept. i.e. blocking people at the connection level with some secret source formula.