mail confusion

[Jay Moore]

On Tue, 2005-11-08 at 00:12 -0600, Les Mikesell wrote: 
> On Mon, 2005-11-07 at 22:55, Jay Moore wrote:
> 
> > Bottom Line: Having found this trove of knowledge, I *think* my best
> > course of action is to fix (right after I find it) the sendmail startup
> > to remove the "-bd" option, then start hacking submit.mc to fix my
> > original problem.
> 
> No, the only thing you need it fix is if you want to accept mail
> on addresses other than 127.0.0.1 and sendmail's idea of your
> hostname if it isn't what you want as a return address.

But that's just it - I *don't* want to accept mail on addresses other
than lo (127.0.0.1). On this machine, I get my mail from a "real" (i.e.
Internet DNS-resolvable) server via POP3. I only want to send mail from
this host

> > > Also, check to make sure your host name really is what you think it
> > > is, by typing
> > > 
> > >   $ hostname
> > 
> >         [jamoore at aria ~]$ hostname
> >         aria.cullmail.com
> > 
> > I don't think it makes any difference to the receiving mail server
> > whether or not aria.cullmail.com is an Internet-DNS-resolvable host...
> > in any case, the connection will go through my firewall, and appear to
> > come from that host.
> 
> Most smtp receivers these days will not accept email if the
> sender's domain is not DNS-resolvable.  Some sites will also
> refuse it if the IP and DNS don't match, but that is less
> common (and the RFC's explicitly permit that case - otherwise
> multihomed hosts wouldn't work).

That's the problem - localhost.localdomain is not DNS-resolvable. 

The most confusing thing to me now is this: if I send a message as a
normal user from the 'mail' command line, it gets delivered just fine;
the From: line in the header reflects that the message is from
'localhost.localdomain', but the receiving mail server sees it as
ultimately from my NAT'ing firewall (frwl.cullmail.com).

However, if I send the message from the root account, it gets rejected
by the destination host - the receiving host sees a From: header of
'localhost.localdomain'.

Why is this? Why is mail from root handled differently than mail from a
regular user?

Thanks,
Jay