[Exim] Authentification or not

Hello,

I'm new in using exim.

I have installed v3.12 on a Debian potato with Linux 2.2.14.

I have a running configuration with authentification by searching in
the /etc/shadow for user and encrypted password.

But I have some users that shall use exim for relaying and their
software isn't able to authentificate. As a replacement for auth. I
want to check their IP numbers AND the domain of their sender
address. The IP number will be a range because they use an ISP.

Today I read the documentation and made some tests on a local
maschine.
But it don't work! :-(
So I created with eximconfig a new exim.conf without auth. so
I was able test some parameters.

Here are some questions after doing that:

The local maschine which should simulate the login over an ISP
has the address 194.221.67.85. I use Netscape Communicator
for testing.

When I set this address to
host_accept_relay = localhost : 194.221.67.85
I can send an e-mail. But
host_accept_relay = localhost : 194.221.67.0/255
don't work? What is wrong?

Why checks
relay_domains = ...
the recipient address too? I though that this parameter says FROM
which domain I am able to send and not TO which domain?

And
sender_address_relay = *@sector.de
? Is that correct after activating
sender_verify = true
?

But my biggest probleme is that the changes made in the configuration
without auth. don't work in the config with auth. until I deactivate the
auth. driver! :-(

Can you give me some hints to realize the "authentification" by IP address
and sender domain for that users that are not able to authentificate beside
the real auth.?

Best regards

Michael M"uller