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Subject: Re: Incessant Bounces
From: Brad Knowles (blkskynet.be)
Date: Wed Aug 23 2000 - 12:24:47 CDT

At 12:23 PM -0400 2000/8/23, Greg A. Woods wrote:

> If the MTA sends a 5xx series response to either HELO or "MAIL FROM:"
> (or presumably to "RCPT TO:"), then the result is *NOT* lost mail!!!!!

        Yes, it is.

        The mail was not delivered when it should have been (because of a
transient error, perhaps on the recipient side), and therefore I
would certainly consider it to be "lost". Had a 4xx response code
been given instead and the mail message tried again, the transient
problem may have been cleared, and the message might well be
delivered just fine.

> So, where oh where are you getting the idea that permanent SMTP errors
> are "unsafe" in any way!?!?!?!?!

        Personal experience. Ever run a site that handled millions and
millions of mail messages per day? Ever run a site that handled
e-mail for millions and millions of users? I didn't think so.

        Simply put, when you get that high up into the
stratosphere/troposphere/ionosphere or out into space (where no one
else in the world has ever gone), there's just some really weird shit
that happens, no one knows why or how, and the only thing you can do
is do the best you can to try and protect yourself from it.

        Now, the reality of it is that really weird shit like this
sometimes happens considerably less frequently when you are closer to
the ground, but it still happens. The only difference is that you're
not handling millions and millions of mail messages for millions and
millions of users every single day, so this "one in a million"
occurrence isn't frequent enough for you to notice it or identify it,
while for the bigger sites it happens often enough to get a serious
number of daily complaints filed, and which get dumped on your desk.

   These are my opinions -- not to be taken as official Skynet policy
Brad Knowles, <blkskynet.be>                || Belgacom Skynet SA/NV
Systems Architect, Mail/News/FTP/Proxy Admin || Rue Colonel Bourg, 124
Phone/Fax: +32-2-706.13.11/12.49             || B-1140 Brussels
http://www.skynet.be                         || Belgium

"They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." -Benjamin Franklin, Historical Review of Pennsylvania.