Recently I encountered a problem with SSL on one of my websites … some web browser could not connect securely.

When I ran a test from Linux, I got the following error:

OpenSSL: error:1408E0F4:SSL routines:ssl3_get_message:unexpected message

After a bit of digging, I found that a recent upgrade to the certbot-auto tool, that creates LetsEncrypt certificates, caused the problem.

The fix was to modify /etc/letsencrypt/options-ssl-apache.conf so that the SSLSessionTickets setting was set to on.