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Re: OT: 5xy - Do we need a "I MEAN IT!" do not retry response code?

2007-05-02 13:21:42

On Wed, May 02, 2007 at 08:54:55AM -0400, Hector Santos wrote:

Peter J. Holzer wrote:
On 2007-05-02 05:28:16 -0400, Hector Santos wrote:

I'm not sure either. "hard and soft bounces" could be either 5xx and 4xx
respectively, or a "soft bounce" could be a "couldn't deliver for $n
hours, will keep trying" message.

It kind of sounded to me that hard was "for sure rejects" at the SMTP 
level, and soft being "Bounceback Messages" or NDNs.  But in either 
case, it tries 3 times before it moves the email address to the 
do-not-send list. :-(

I work for an ESP. So while I can only speak for my company, I'm pretty
certain that most ESPs honor 4xx and 5xx at the MTA level. Eventually a
message with a 4xx will either be delivered or expire. At that point
the resulting bounce, whether it is a bounce that happended during SMTP
or an out of band bounce that happens after issuing a 250 and then
later sending a NDN[1] (like AOL use to do), an ESP can not just use a
4xx/5xx[2] code to determine whether that email should be removed from
a subscriber list. They have to go to the text portion and make a
determination from that. Consider the following examples:

This would cause an addition to do-not-send list:
550 Unknown User

while these would not:
550 Over Quota
550 5.7.1 Spammer!
550 Spam phrases found

If a mail server is issuing a policy reason, the assumption being made
is that the next message that is sent will not violate the policy. That
is because the next message will contain different content. The
previous message could of been blocked in error. Think of a large drug
company - Merck(?) - and one of their biggest selling products in which
an investor gets a monthly newsletter talking about sales.

I do agree the ESP industry needs to move away from hard and soft when
referring to list maintenance. I typically use permanent and temporary
undel.

I don't think we need a 'I mean it'. I think we need a way to say 'no
more mail will be accepted from this mailstream'. This is to help when
a receiver has decided to block all email from a certain IP or domain.
No sense in having a sending MTA keep sending email. Obviously that is
currently out of scope.


-- 
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