2018年10月31日付で、Microsoft Office 365 は TLS 1.0 および 1.1 のサポートを終了します

[Falco]

そして、TLS 1.3 は

Discourse new Base Image

We just released a new base image with support for TLS 1.3 . [image] Users will need to rebuild from the command line to get this new feature. We also packed a few dependencies update, moved from Ubuntu 16.04 to Debian Buster and updated our SSL cyphers list to match https://ssl-config.mozilla.org/ intermediate config and updated to Ruby 2.6.4. Due to all that we will make the command line rebuild mandatory later this week.

以降です。