How to debug nullmailer

Hi all,

I'm running nullmailer on Ubuntu 10.04 LTS, and can't get it to mail, 
and get seemingly infinite error messages. I need to know what steps 
to take to troubleshoot this, and especially how to locate the 
nullmailer queue, which I suspect has some bad stuff in it.

I don't really know how to use nullmailer after going through the info 
on /usr/share/doc/nullmailer and googling.

Here's what happens when I run nullmailer-send as root:

===========================================
Sending failed: Permanent error in sending the message
Starting delivery: protocol: smtp host: mail.a3b3.com file: 
1309464266.3980
smtp: Failed: 550-Verification failed for <[email protected]>/550-
The mail server could not deliver mail to [email protected].  The 
account or domain may not exist, they may be blacklisted, or missing 
the proper dns entries./550 Sender verify failed
===========================================

When I run mailq as root it gives me a long or infinite list of 
messages like this:

===========================================
2011-03-04 22:04:26 798 bytes from <[email protected]>
  to <[email protected]>
===========================================

I looked all over my machine, did:

locate nullmailer

and couldn't find the queue in order to troubleshoot this problem.

Thanks

Steve

Steve Litt
Recession Relief Package
http://www.recession-relief.US
Twitter: http://www.twitter.com/stevelitt