[Exim] Verifying recepients

Hi,

I'd like to check, if a recepient really exists before accepting a mail
via smtp.
This is done via ACL, isn't it?

The users do not have local accouts, but need to be looked up in an
ldap-database.

The problem now is:
For example: I have the mailinglist mylist.
It has an entry with uid=mylist in the ldap database.
But I'd like to accept mail to mylist-owner aswell although there is now
such entry in the ldap database.

(how) is that possible?

Thanks in advnce,
Yours, Rudolf