Localized mail servers, global scope

Thu Jun 23 13:07:22 UTC 2005

On Thu, 23 Jun 2005 Michael.Dillon at btradianz.com wrote:

>> You don't need a central MX if each site MTA knows which users are at
>> which sites. Incoming email may have to take an extra hop if it comes in
>> to the wrong site, but that's a consequence of the specification that no
>> implementation can fix.
>
> In other words, SMTP does not have the equivalent of an
> HTTP redirect which is what he wants here. Maybe SMTP
> really is broken? ;-)

HTTP is 100% client-server protocol so redirect is server telling client 
to go somewhere else (which is exactly what HTTP redirect does).

But SMTP is store-forward system like ip itself. In store-forward 
redirection is changing of connection path by intermediate system.
So with ip this is handled by routers and transparent proxy servers.
In SMTP this is handled by forwarding systems which change mail
transmission connection and redirect and pass message somewhere else.

So we do have redirect functionality SMTP, its just not done same
way as HTTP because of differences in system infrastructure.

P.S. Somewhat related work of mine:
  http://www.elan.net/~william/emailsecurity/draft-leibzon-emailredirection-traceheaders-01.html

-- 
William Leibzon
Elan Networks
william at elan.net