[Exim] SMTP AUTH problems

I decided to try the latest Exim release and learn about SMTP AUTH.
Here my experience:

The given perl script to encode the AUTH parameters does not work as
expected, because the parameters are encoded null terminated. This
script generates the needed string:

#!/usr/bin/perl
use MIME::Base64;
printf ("%s", encode_base64("\0uid\0password"));

Note that the MIME package is not installed by default.

I used the above script successfully to authenticate using AUTH PLAIN
and an LDAP lookup to authenticate users. But as soon as Exim offered
authentication, I had a bad surprise.

The netscape messenger insists on authenticating, if the server offers
it! Suddenly a window pops up and asks for uid and password if people try
to send mail. Yet worse, there does not appear to be a way to disable
authentication. I already found out that netscape silently throws
an @ with anything behind it away in POP3 logins, but this beats it.
Thank you, netscape. >:-|

This does not allow a soft migration to authenticated SMTP by extending
the Exim configuration and slowly tell people to use it to gain access
to extra services.

Right now, the only way I see is to add a virtual network interface and
run two exim instances, one without AUTH support on the first interface
and one with AUTH on the second. Everybody but those who wish to
authenticate uses the first interface (mx.domain) and the rest uses the
second (mxauth.domain). Very ugly. Can I run two instances of exim that
have different config files but the same spool directories and logfiles?

I appreciate any different solutions to this problem.

Michael