A mail delivery puzzle

[nmeyers at javalinux.net (Nathan Meyers)]

On Wed, Sep 18, 2002 at 11:39:57PM -0400, Bill Horne wrote:
> Thanks for reading this.
> 
> I have a ham radio domain name, namely "w1ac.ampr.org". The ampr.org domain
> is used by ham operators to lookup addresses in the 44.0.0.0/8 space, which
> is a semi-detached network connected via amateur packet radio.
> 
> Now, the problem: I have an MX record in the ampr.org dns, which points to
> billhorne.homelinux.org, the dynamic dns domain name for my Linux firewall.
> If I send email from either netscape.net or hotmail, to
> <user>@w1ac.ampr.org, it gets through OK. I have set the new domain in the
> sendmail.rc file, so sendmail knows it's supposed to take mail for
> w1ac.ampr.org (and indeed it does, from hotmail/netscape). However, mail
> from my attbi.com address produces an error from the attbi.com postmaster,
> saying that "Host w1ac.ampr.org not found".

I can't find any MX records for ampr.org or w1ac.ampr.org; in fact, I
can't find any records at all for the latter name. What do netscape.net
and hotmail know that I don't?

Nathan Meyers
nmeyers at javalinux.net