RE: fake mx in xen subdomain

[Joshua Megerman <qmail@xxxxxxxxxxxxxxxxxxxxx>]

> Now, the primary reason to do this is to gather some data for research and
> possible implementation plus send idiot SMTP sessions that go straight for
> the lowest priority MX to the floor.
>
I don't understand this sentance (and I'm well versed with the SMTP
specs).  Why is a mail server trying to deliver directly to the lowest
priority MX an "idiot SMTP session"?  The whole purpose of sending email
is to have it delivered to the the final destination.  The purpose of the
different MX priorities is to list how far from the final destination any
give mail host for the domain is located.  Since it "costs" more to send a
message to a server that's "farther" from the final destination (because
it requires more server and network resources and takes longer), unless
there are other network reasons for not doing so you should _always_ try
to deliver it to the lowest MX priority (unless you've already determined
that you can't).  Anything else is causing more work to be done to deliver
the message.

Now, you can argue that qmail should try other MX records if the lowest
one doesn't accept the message, but that's been done here before (many
times), and the answer is still the same: The RFC is ambiguous, and while
qmail's implementation may not be the only valid interpretation of the
spec, it IS valid, and therefore MUST be worked around if you want to
receive email from it.  You may choose to configure your MX records in a
way that causes qmail to fail when delivering to it, but that's _not_
qmail's fault - it's yours.  As long as qmail properly handles whatever
response you give it, it's within spec.

That being said, I totally agree with the idea that intentionally setting
up resources to waste on answering connections just to say "go away" is a
total waste.  There are better ways to reduce the spam inflow (greetdelay,
gerylisting, blacklists, others - take your pick (and let's not debate
them her and now)), and none of them break qmail's ability to deliver. 
Think of it this way: would you set up a separate phone line and list it
as your phone # in the phone book just to have the telemarketers and crank
calls go to it?  Sounds pretty sily when you think of it that way, doesn't
it...

Josh

Joshua Megerman
SJGames MIB #5273 - OGRE AI Testing Division
You can't win; You can't break even; You can't even quit the game.
  - Layman's translation of the Laws of Thermodynamics
josh@xxxxxxxxxxxxxxxxxxxxx