[exim] How to configure exim for simplest SMTP authentificat…

Hello everybody,

I have a working exim setup that works fine for receiving emails and
that can also send emails from the command line.

What is still missing is SMTP authentification, so that users can also
send emails from their mail clients. Because we only have 3 users, it
is fine that they share a single username/password for sending email
via SMTP. (for reseiving email of course everybody has their own
account)

So I used this line in Local/Makefile:

AUTH_PLAINTEXT=yes

Then I define the following driver in the configuration file:

   PLAIN:
     driver                     = plaintext
     server_set_id              = $auth2
     server_prompts             = :
     server_condition           = \
       ${if and
   {{eq{$auth2}{OUR_SHARED_USERNAME}}{eq{$auth3}{OUR_SHARED_PASSWORD}}}}
     server_advertise_condition = ${if def:tls_in_cipher }

First question: Is this sufficient and the best/easiest solution to
implement SMTP authentication? Do I need to enable anything for
encryption? (I already use encryption for IMAP, so exim should already
have it.)

Second question: exim recompiles fine with "AUTH_PLAINTEXT=yes", but
when I try to start it (with -bd parameters), it just quits without
any message and without any entry in paniclog, mainlog or rejectlog.
Is there some other way to find out what went wrong? Is there maybe
some obvious setting that I also need in Local/Makefile?

Thanks