[exim] question about acl

I have my acl defined to accept from authenticated connections but i
want to make some basic filtering for

- Forwards can be only configured to send to local domains
Example: local_domains: example.com

My users can set up forwards but the destination of the forwarded
email can be only on example.com

- beside smtp authentication, i want to check (i know this is weak)
that the sender address is one of my local domains.
By now after a successfull smtp authentication, im able to send
messages with any FROM

Thanks in advance.