[Exim] testing string expansion for relay_domains

Lo all,

I was just wondering if there's any good way to test / debug a mysql lookup
type for relay_domains?

I currently have:
relay_domains = mysql;SELECT ZoneName FROM CompanyDNSZones LEFT JOIN
CompanyDetails ON \
                      CompanyDetails.CompanyID=CompanyDNSZones.CompanyID
WHERE CompanyDetails.CompanySuspended='0' AND \
                      CompanyDNSZones.ZoneName='$key' AND
CompanyDNSZones.ZoneServices LIKE '%HasBackupMail%';

Now, how can I verify that the lookup actually works? exim -bt <address>
sends the mail to the primary site due to MX lookups, and thus does not
execute the relay_domains check...

thanks,

--
me