docecot SSL/TLS without certificate

[Ernie Luzar]

Is there some way to configure Dovecot pop3 server to provide TLS 
without Dovecot needing a certificate? The self signed cert that the 
Dovecot manual shows you how to make is flagged as invaild / un-trusted 
every time my thunderbird mail reading client fetches mail and I have to 
answer question about accepting it.

I see Dovecot has option to require client to also have a certificate 
but no where does the Dovecot manual talk about what this certificate is 
or how to build it. Will importing the Dovecot certificate to 
Thunderbird stop Thunderbird from issuing that invaild / un-trusted 
certificate error message?