I have a question about Thunderbird.
I am not sure if I am in the right forum, maybe this should be in security forum.

On server settings of the account there are the security options
use SSL
use secure authentication.

SSL works without problems but when I use secure authentication I get this error
"website certified by an unknown authority"

If I use SSL will the entire communication between the server and client encrypted ?

What does secure authentication do exactly ?
Is it to make sure that you connect to the server you think you are connecting ?

kind regards