Hi, I read few posts about this issue but none seems to work 
My domain bluepek.com works fine with the mail-server on my VPS. From there I’m able to send and receive emails. The DNS records looks good to me, but Thunderbird is unable to exchange emails from this domain.
I’ve MX record, SSL is Strict, and all ports are open.
When I try to add an exception for mail.bluepek.com, TBird says it’s not required because the domain provides a valid certificate.