Connection to mail over SSL fails

Overview IMAP, POP3, and SSL that connect over SSL either via STARTTLS on port 143/110/587 or 993/995/465 respectively fail with a certificate warning without any symptoms prior to October 25, 2016. Symptoms include the following dialog from Thunderbird: Cause With the proliferation of free SSL certificates via Let’s Encrypt,┬ávendors have begun to tighten requirements on…