can't configure authentication in exim

[Francesc Oller <francesc@ferran.upc.es>]

Hi all!

I'm trying to configure exim 3.35 as relying to a outgoing smarthost 
which
uses PLAIN AUTH. Lines from /etc/exim/exim.conf (transport, router and
client authentication respectively):
#---------------
# This transport is used for delivering messages over SMTP connections.

remote_smtp:
  driver = smtp
# authenticate_hosts = smarthost.isp.com
  authenticate_hosts = correu.upc.es

# Send all mail to a smarthost

smarthost:
  driver = domainlist
  transport = remote_smtp
  route_list = "* correu.upc.es bydns_a"

login:
  driver = plaintext
  public_name = LOGIN
  client_send = ": francesc oller : my_passwd"
#--------------

While I can send mail manually via telnet, sending commands AUTH LOGIN,
base64("francesc oller") and base64("my_passwd"), exim fails to deliver
with an 505 Authentication required error. Lines from /var/log/exim/
mainlog:

#--------------
2003-07-21 19:19:30 19eeJu-0000Ph-00 <= francesc.oller@upc.es U=francesc
P=local S=325 T="a correu"
2003-07-21 19:19:31 19eeJu-0000Ph-00 ** francesc@entel.upc.es 
R=smarthost
T=remote_smtp: SMTP error from remote mailer after MAIL
FROM:<francesc.oller@upc.es> SIZE=1358: host ackerman.upcnetadm.upcnet.
es
[147.83.2.243]: 505 Authentication required
2003-07-21 19:19:32 19eeJw-0000Pm-00 <= <> R=19eeJu-0000Ph-00 U=mail 
P=local
S=1252 T="Mail delivery failed: returning message to sender"
2003-07-21 19:19:32 19eeJu-0000Ph-00 Error message sent to
francesc.oller@upc.es2003-07-21 19:19:32 19eeJu-0000Ph-00 Completed
2003-07-21 19:19:33 19eeJw-0000Pm-00 ** francesc.oller@upc.es 
R=smarthost
T=remote_smtp: SMTP error from remote mailer after MAIL FROM:<> 
SIZE=2308:
host ackerman.upcnetadm.upcnet.es [147.83.2.243]: 505 Authentication
required
#--------------

It seems as if either exim doesn't first authenticate to server (but
authenticate_hosts = correu.upc.es is set) or authentication code isn't
built in, but exim -bP authenticators says:

#--------------
login authenticator:
driver = plaintext
public_name = LOGIN
server_mail_auth_condition =
server_set_id =
client_send = : francesc oller : my_passwd
server_condition =
server_prompts =
#--------------

Sadly to say M$ OutLook Express sends mail well, provided 
"authenticate  when sending" box is checked

Any clues?

Francesc Oller

Please CC your answers to francesc.oller@upc.es. Thanks.