Help on CRAM-MD5

Howdy,

I'm using dovecot and mysql users, and i'm creating the password with:

ENCRYPT('some-passwd',CONCAT('$6$', SUBSTRING(SHA(RAND()), -16)))

So far so good, everything's fine. Today saw that i didn't enabled CRAM-MD5, but if I do, and the (at least) IMAP client (roundcube/thunderbird/etc) issues CRAM-MD5 it doesn't authenticate. What am i doing wrong, or that can be done so that all types work (SASL PLAIN LOGIN + CRAM-MD5)?

Thanks in advanced,