[exim] exim3: host_auth_accept_relay and rbl_domains

Dear List

I have set up some RBL blocking in my exim v3.36 and I use
authentication for my users to send out mails. Unfortunately it seems
that blacklists from rbl_domains take preference over
host_auth_accept_relay and thus certain authenticated users cannot send
eMails with an error "Host is blacklistet" and get it gets an entry in
the reject log. The settings I used are:
host_auth_accept_relay = *
rbl_domains = ...
rbl_hosts = ! 127.0.0.1/32

Is this related to misunderstanding the features or is this an
unintended behaviour of exim?

To solve the problem, I tried to set
rbl_hosts = \
${if eq {$authenticated_sender}{} {$sender_host_address}{}}} : \
! 127.0.0.1/32
...but I couldn't really test, if it is working proberly.

Did anyone else encounter this problem? How would you solve it?

Thank you, Adrian.