[Dovecot] configured mechanisms don't work

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