[Mailman-Users] Bounce issues with Yahoo

Brad Knowles brad at stop.mail-abuse.org
Fri Mar 3 20:54:23 CET 2006

At 11:08 AM -0800 2006-03-03, Harold Paulson wrote:

>  ...for your resume first, and was suggesting a solution I thought was
>  both useful, and more...correct.

	You were saying that a non-existant magic mechanism should be 
used for the MTA to know exactly how the MLM would react to a given 

	That's what I was shooting down.

>                                    I did meet Eric Allman once.  He
>  seemed nice.

	I've met Eric on several occasions, and I like to think that I've 
had a pretty good relationship with him and the company -- since 
before the company existed.

>>  	Please provide evidence for your claims.
>  You will have to forgive me because I have only been on the `net for a
>  minute or two, and never worked for AOL, but don't you sort of water
>  this down below and - at the perilous risk of putting words in your
>  mouth - agree that this is entirely possible, but, maybe a little work?

	Not really.  As I said, a policy daemon solution won't work very 
well -- you have to use an SMTPD_PROXY or LMTP solution instead.

	In either case, you don't have a pre-existing magic mechanism 
where the MTA automatically knows precisely how the MLM will react to 
a given message.  Instead, you've got a lot more work ahead of you to 
make use of a mechanism that MTAs may make available, but which has 
never existed for Mailman.

>>  	That would be nice, but Mailman does not, in fact, maintain such a map.
>>  It has a procedure that it goes through to determine if the user is a
>>  subscriber or should otherwise be moderated or the message should be
>>  rejected, but there is no easy "map" for this process.
>  Ok, maybe it's not an MTA-ready map, but Mailman looks up the sender in
>  it's subscriber database when it gets a message to a members only list,
>  right?

	That's a small part of the process, yes.  There are lots of other 
parts that you are ignoring.

>          That code exists?  And could be adapted, in a fairly
>  straight-forward manor to do exactly the same thing a few seconds
>  earlier, before your message hits disk?

	Could be adapted -- yes.

	Fairly straightforward manner? I don't know.

	I'm not a programmer, but I think it would probably be 
"Non-Trivial" to adapt that code.  However, I would be happy to be 
proven wrong.

>>  	Sure, anyone can write an SMTP or LMTP-like engine that internally
>>  goes through the processes that the MLM would normally go through, and
>>  be able to provide that information to the MTA through a proxy service,
>>  but the MTA would also have to be configured to hold the sender open
>>  while checking the proxy -- again, most MTAs are not configured to do
>>  this, and for lots of good reasons the MTA authors suggest in the
>>  strongest possible terms that you not make the mistake of configuring
>>  their software in this way.
>  Seems like you are imagining a lot of unnecessary plumbing.

	Demonstrate to me that you have a level of understanding of the 
problem equal to Eric Allman, Wietse Venema, Barry Warsaw, Tokio 
Kikuchi, or Mark Sapiro, and I might be willing to believe you.

	Otherwise, you're going to have to prove it to me by actually 
doing it.  Then tell me what you did, and how easy it was.

>  When you have the sender address during SMTP
>    If it's going to a known Mailman list address
>      If the sender address can't be found in the list subscriber db
>        Say no thanks...(or say please try again later)
>  Mailman will do all of this a second or two later anyway, right?

	Again, the connection would have been dropped by then.  That's 
why you have to cook up a complete LMTP interface for Mailman.

>  Well you know of course I was trying to goad you into writing it.  I
>  don't know Python, or have a problem with backscatter.  :)

	I'm not a programmer.  That's something I've said more than a few 
times over.

	I do have a fairly deep operational understanding of Internet 
e-mail and mailing list management systems, and I can give you plenty 
of tips and pointers of things you might need to do if you were going 
to try to build a Yahoo! or AOL-size mail system, or a mailing list 
management system of that scale.

Brad Knowles, <brad at stop.mail-abuse.org>

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."

     -- Benjamin Franklin (1706-1790), reply of the Pennsylvania
     Assembly to the Governor, November 11, 1755

  LOPSA member since December 2005.  See <http://www.lopsa.org/>.

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