[exim] mx_any not expanding

Is there a way I can find out what mx_any is expanding to?
I have a system running cpanel, using exim for MTA. I finally got an ACL
written that will block incoming mail unless there is an MX record for the
recipient. Unfortunately, all emails are being blocked, including the one
domain we opened up by pointing an MX record to this box.

We use /etc/resolv.conf to point to our nameservers, but I don't know how to
see what @mx_any resolves to.

Is there a way to debug this by printing the contents of @mx_any?

here is the domainlist definition I am using

domainlist local_mx_domains = @mx_any/ignore=127.0.0.1

and I added this to check_recipient:

# Drop those not having an MX record for Recipient drop message = That is
not a valid email for this domain !domains = local_mx_domains

Any ideas?
Thanks