Gateway to python-list is generating bounce messages.

Steven D'Aprano steve at
Fri Sep 12 14:29:12 CEST 2008

On Thu, 11 Sep 2008 17:27:33 +0200, Sjoerd Mullender wrote:

> When mail messages bounce, the MTA (Message Transfer Agent--the program
> that handles mail) *should* send the bounce message to whatever is in
> the Sender header, and only if that header does not exist, should it use
> the From header.

Who makes up these rules, and why should we pay the least bit of 
attention to them?

It's one thing to say "right or wrong, that's what list admins do and you 
have to deal with their behaviour whatever way you can". It's another 
thing altogether to take the legalistic attitude of "never mind the 
consequences, the standard is the standard and must be unthinkingly 
obeyed". If the standard does more harm than good, then ignoring the 
standard is the right thing to do. (Better would be to change the 
standard, but that probably won't happen until there's a critical mass of 
people who ignore the existing broken standard and form their own de 
facto standard.)

A standard isn't "correct" just because it's a standard, it's merely 
something that a committee has agreed to do. In other words, it's a 
compromise. Now, such compromises might be good and useful, or they might 
combine the worst of all opinions. Just because something is standardized 
doesn't make it the right thing to do. If you want proof of this, I give 
you the recently approved ISO standard for Microsoft's so-called "Office 
Open XML" OOXML file format.

The standard behaviour of sending bounce and out-of-office messages to 
the sender works well when sending email to individuals, but for mailing 
lists it is pointless and counter-productive. Pointless, because the 
sender can't do anything to fix the problem he's being notified about. 
And counter-productive, because it is an anti-feature, something that 
makes the mailing list more unpleasant and less useful. Anyone who has 
regularly emailed to a large mailing list has surely experienced the 
frustration of receiving bounce messages from perfect strangers.

To anyone who wishes to defend the process of sending mailing list 
bounces back the sender, ask yourself this: what do YOU do with such 
bounces when you receive them? If you ignore them or delete them (whether 
manually or via a procmail recipe or some other automatic system) then 
what benefit does the standard behaviour offer?


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