[Dovecot] configured mechanisms don't work

[Eggert Ehmke]

Hi,
I am new to this list and to dovecot. Forgive me if I ask long discussed 
items. 
I managed to install postfix and dovecot 1.0.rc15 on a Debian Sarge server out 
of the backports. It works so far, I can send emails via smtp to postfix, 
they are stored in the virtual mailboxes of some users, and I can get them 
via IMAP from dovecot. However, in dovecot.conf I configured

      mechanisms = plain login digest-md5 cram-md5

when I connect to the server via telnet 143, I get this:

2 CAPABILITY
* CAPABILITY IMAP4rev1 SASL-IR SORT THREAD=REFERENCES MULTIAPPEND UNSELECT 
LITERAL+ IDLE CHILDREN NAMESPACE LOGIN-REFERRALS STARTTLS LOGINDISABLED
2 OK Capability completed.

So I can't authenticate using cram-md5. What may I be missing?

Regards & happy new year!
Eggert