[Exim] remote host is local host

Hi,

I hesitate to ask this because I suspect the answer is pathetically
simple, but I have not found it in the documentation or list archives.

I run exim on an IPChains firewall. Behind the firewall/mailhost, I
have an IP-Masqueraded private class C network that can access the
Internet. I receive mail on the firewall and access it from within the
network with imap.

Although I can ping the hosts on the private network from the firewall,
I cannot send mail to them with exim. If I try, the mail is frozen and
exim says, "remote host address is the local host."

What am I missing?

sbt