[exim] ACL problem

Hi

I have a problem with acls regarding sending mail from the localhost.
ie. via a webmail application. I can telnet on port 25 to the machine
from a remote host and the acl works. But when I use the webmail app or
run a test mail from the command line, it fails.
I want to allow the sending of mail to one particular host. I am using
a very slightly modified default exim.conf and exim 4.43.

Can anybody give me any pointers as to why my acl only works from a
remote host.

I've been wrestling with this for about a week on and off, and I really
dont want to start moving the webmail app to another server.

Thanks for any response

Kev