Dovecot and thunderbird authentication issue?

[David Mehler]

Hello,

I'm using Dovecot 2.2, Postfix 3.5, and am atempting to get the latest
version of Thunderbird to work. I tried account autoconfig which did
not work, so I had to manually enter information and correct other
information. On my server dovecot supports plane and login
authentication methods but only over starttls i've got a letsencrypt
certificate. My thunderbird configuration looks good, right hosts for
incoming and outgoing mail, right ports, 143 starttls, and 587 smtp
submission, and thunderbird has the authentication method set for
normal password. This I interpreted to mean thunderbird is going to
starttls then send the username and password. Thunderbird is giving me
this error:

imap server does not support the selected authentication method

I realize this is vague, any suggestions?

Thanks.
Dave.