How to stop a cascade of mail delivery failure messages

Matt Brodeur mbrodeur at NextTime.com
Wed Dec 15 14:49:00 EST 2004


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On Wed, Dec 15, 2004 at 11:35:36AM -0500, Dan Coutu wrote:

> So first let me ask, does sendmail actually work this
> way, with no limit on ping-pong bounces?

   What SHOULD happen is that the second bounce (the double-bounce)
gets sent to postmaster@ instead of the invalid user.  So in your case
it should look like:
   Spammer forges invalid at client to invalid at random.foo
   random.foo bounces "User Unknown" to invalid at client
   client bounces the bounce to postmaster at random.foo

   Now, if someone's bouncing postmaster mail I'm not sure what will
happen. 


> If it does then there must certainly be a way to stop it, such as
> silently dropping failed mail.

   You can configure a custom delivery address for double-bounces.  In
some places I've used this in the sendmail.mc:

dnl # Drop all double-bounces.
dnl # Either supply an address (postmaster) or null string to drop.
define(`confDOUBLE_BOUNCE_ADDRESS', `')dnl

   I'm not sure what this translates to in .cf syntax.  It's something
frightening, I'm sure.

- -- 
Matt Brodeur                                                       RHCE
MBrodeur at NextTime.com                           http://www.NextTime.com

Hard work has a future payoff. Laziness pays off now. 
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