Hello,
I have run into this problem too. I had allowed all sasl_mech_list (option commented), so thunderbid tried NTLM first and failed. So I put "sasl_mech_list: PLAIN LOGIN CRAM-MD5 DIGEST-MD5". (NTLM caused many false failures with imap anyway), thunderbird started using DIGEST-MD5, at which point it at least allowed me to see the list of calendars, and let me to add it. But it did not sync the calendars and asked for password indefinitely.
My android app (davx5), works fine, as it is using basic auth anyway... Same with thunderbird addon cardbook...
I added https_sasl_mech_list: PLAIN and voila, thunderbird accepted the password and synced the calendar.
Now it works perfectly.
Best Regards
Vladislav Kurz
