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Re: SMTP traffic control

2011-10-24 09:42:54

On 24/10/2011 14:49, Murray S. Kucherawy wrote:
-----Original Message-----
From: Rosenwald, Jordan 
Sent: Monday, October 24, 2011 6:07 AM
To: Murray S. Kucherawy
Cc: ietf-smtp(_at_)imc(_dot_)org
Subject: RE: SMTP traffic control

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)?
[So that's what that button does.]
Right, and I believe the goal is an optimization that reduces retries that are 
doomed to fail.  The question you could probably answer from your perspective 
is whether or not those retries are a problem for you, either as a sender that 
provides queueing services for customers, or as a receiver that periodically 
temp-fails for resource reasons.  Standardizing the reply increases the 
likelihood that clients will adhere.  But if the current setup isn't a pain 
point for you or others, then that suggests there's not really a problem here 
worth solving.

We get 'pain' from these limits, but mainly on customer facing submission servers ('smarthosts'), rather than MX servers. It would be good if we could easily tell that a '4yz' error we got was due to trying to send 6 messages in a single session (when we could immediately start a new session) rather than it being due to the server's disk being full (in which case immediately starting a new session would be pointless)

I haven't come across it much in MX servers, but that could be because most of our customers are small businesses, so sending large numbers of messages to a particular MX server is unlikely, and the automatic retries probably mask the few cases where it happens.

(Of course we have bigger 'pain points' - the '10 errors and we'll drop you' is the worst:
rcpt to:<invalid(_dot_)address(_at_)bad(_dot_)domain(_dot_)com>
4yz invalid recipient
rcpt to:<another(_dot_)address(_at_)another(_dot_)bad.domain>
4yz invalid recipient
... 8 more times
4yz too many syntax errors, connection dropped

(now a message in the outbound queue which will never go)
but that's off topic)

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