[exim] Exim to only allow mail from one SMTP server.

Hiya

Im trying to get Exim to only allow mail from one SMTP server. I run
Debian Lenny.

What I have done is.

Created /etc/exim4/conf.d/main/000_localmacros, which contains

LOCAL_DENY_EXCEPTIONS_LOCAL_ACL_FILE=/etc/exim4/denyhosts

LOCAL_DENY_EXCEPTIONS_LOCAL_ACL_FILE is the macro I got from
/etc/exim4/conf.d/acl/20_exim4-config_local_deny_exceptions

/etc/exim4/denyhosts, then just contains,

deny hosts = ! mail1a......
      message = May not SMTP

If I test with
exim -d+acl -bh anothermta.com

I get

processing "deny"
check hosts = !mail1a :
gethostbyname2(af=inet6) returned 4 (NO_DATA)
gethostbyname2 looked up these IP addresses:
name=mail1a. address=1xx.7.18.2xx
host in "!mail1a. :"? yes (end of list)
deny: condition test succeeded

But I still get a 250 Accepted.

I could use iptables to allow the MTA, but I thought it would be better
if it were Exim controlled / managed the process.

If someone could help me, it would be most appreciated.

Kind Regards
Brent Clark