[Dovecot] Since Updating Dovecot - Problem by connecting with Client

[Mailing]

Hi,

in the last days I've updated my dovecot on my Gentoo System. Before all
went fine. Since the update it doesn't work in any way.
After the Update my Thunderbird Client says: The Connecction could not
proceeded because it was rejected. Another message was, that I should
use TLS or SSL to connect. I've not changed my config - probably the
update does - and it's only a simple configuration in my home-network.

Has anybody an idea which is causing the problem?

the config looks like this:

protocols = imap imaps
listen = [::]
default_mail_env = maildir:%h/.mail
mechanism = plain

Thx for help

k1x