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Re: SMTP traffic control

2011-10-24 10:03:24

Rosenwald, Jordan wrote:
I don't think I'm squashing such an idea (standardization is usually 
beneficial). I'm more asking, IF we standardize what benefits do we expect 
given that many large ISPs do provide much of the feedback (just not in a 
standardized format)?

The question you asked at the end of your email is substantively different from my 
interpretation of the thread previously, so let me try to answer it: Most ISPs I'm 
familiar with are conveying the information through an over-use (perhaps 
"abuse") of 4xy errors, where several return codes may require reading the 
plain-text content to discern the variations in the responses.

Jordon, the proposed GREYLIST SMTP extension addresses in section:

where the goal is to distinguish between loading limiting rejections and greylist rejections using the proposed "retry=time" hint. This will help the MTA to better decide between a next hop MX/IP immediate attempt or a reschedule delay. Because of the impact Greylisting, we had to change our MTA logic to make all 4yz responses force a reschedule retry.

Its been suggested the extension should consider additional tags for 421 greeting responses such as:


But moves the extension in a more expanded direction and in addition, the MX already has the information in its DNS queries. IMV, any server hint for a mx should not be outside the group already collected.