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Re: Postfix setup



also sprach Matthew Weier O'Phinney <matthew@weierophinney.net> [2002.10.15.1520 +0200]:
> I beg to differ. With services such as those offered by dyndns.org, you
> *can* be an internet site with regards to mail delivery (and any other
> web service, for that matter). And don't try and tell me differently --
> I'm on a dynamic IP and have my domain registered and pointing to it.

Then you are working on the assumption that mail servers who try to
contact you properly work according to RFC 821.

Consider, for instance, the following scenario:

- You go online, IP is 1.2.3.4, dyndns registers it as matt.dyndns.org
- Mail works
- Then you are disconnected.
- Two seconds later, or five minutes, another customer of your ISP
  connects and gets your previous IP 1.2.3.4. He also runs
  a mailserver.
- Someone sends a message to your domain.
- The relaying mailserver does a DNS lookup, and matt.dyndns.org still
  points to 1.2.3.4.
- The relay contacts the mail server at 1.2.3.4, which will most
  likely bounce the message with a "relaying denied" error.

I know that it *mostly* works with dynip services, but it is not
without problems. I would never run a productive machine doing mail on
a dynamic IP without QDMR.

-- 
 .''`.     martin f. krafft <madduck@debian.org>
: :'  :    proud Debian developer, admin, and user
`. `'`
  `-  Debian - when you have better things to do than to fix a system

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