> -----Original Message-----
> From: Brian Candler [mailto:B.Candler@pobox.com]
> Because there's no way, in general, for it to learn that information.
> Consider the very common case when the client host is
> 192.168.0.1, is sat
> behind a DSL NAT router, and the public external IP address
> is assigned
> dynamically by the ISP.
Poppycock. There are various ways, but they require work to set up. If
someone doesn't want to put forward the effort, they shouldn't be running a
mail server.
Check out, for example, dnsalias.net. They have various clients that can
grab address information from NAT boxes and keep a domain name pointed at
the proper IP, automatically.