[exim] Submission mode complications.

I'm certain that there is something that I'm missing, but I'm failing
to come up with what it might be.

if I send a message from the local host, the message is properly
sent. This is not a problem.

If I send the message from my MUA remotely
* Authentication occurs normally and is accepted.
* I get a log message: "remote host address is the local host:
xxx.yyy.zzz (while verifying <foo@???> from host
([xxx.xxx.xxx.xxx]) [xxx.xxx.xxx.xxx]:ppppp)" where xxx.yyy.zzz is
indeed the hostname of the machine the MTA lives on. the first
xxx.xxx.xxx.xxx is the IP of the MUA machine (NAT'd address), Second
xxx.xxx.xxx.xxx is the exposed IP. that all looks fine. The MUA ip
is definitely NOT the MTA's IP. So, I'm a bit confused as to why
that is happening. And I think it is leading to the other messages.
* sender verify defer for <rzigweid@???>: remote host
address is the local host
* temporarily rejected RCPT <dest@???>: Could not complete
sender verify

I have a nasty feeling that there's something obvious that I'm
missing that changes with submission mode. I've also tried debugging
with exim -d -bt, and when specifying dest@???, I get the
expected positive results.

Thank you for any assistance.