[exim] AUTH PLAIN problem with Alpine

Hi,
I'm an heavy user of both Thunderbird (GUI) and Alpine (CLI). But while
I can send email with the former, I cannot with the latter.

Turning debug on on Alpine showed that Alpine sends "AUTH PLAIN"
(without data), and seems to expect prompts. Exim answers "535 Incorrect
authentication data". Based on this, I searched the Internet and indeed
I found this page:
http://www.programdoc.com/447_105_1.htm

According to this page, the RFC would agree with Alpine's behaviour. How
should I change my authenticator so that both Thunderbird and Alpine can
authenticate? It currently looks like this:

plain_courier_authdaemon:
   driver = plaintext
   public_name = PLAIN
   server_condition = \
     ${extract {ADDRESS} \
               {${readsocket{/var/run/courier/authdaemon/socket} \
                            {AUTH 
${strlen:exim\nlogin\n$auth2\n$auth3\n}\nexim\nlogin\n$auth2\n$auth3\n} 
}} \
               {yes} \
               fail}
   server_set_id = $auth2
   .ifndef AUTH_SERVER_ALLOW_NOTLS_PASSWORDS
   server_advertise_condition = ${if eq{$tls_in_cipher}{}{}{*}}
   .endif

Cheers,
Yves.