Components that use JavaMail unable to use TLS 1.2+

User chris_rodman in Mattermost reports:
Our Mail Transport Monitors no longer work. They're trying to connect to Office 365 (smtp.office365.com). It's my understanding that Microsoft no longer supports TLS 1.0/1.1. It' also my understanding that JavaMail has to be upgraded in order to use the newer TLS 1.2 version. If I'm reading the poller.log correctly my OpenNMS instance (v28.1.0) is using JavaMail 1.4.5. Is there something I should be doing to change this? I don't want to inadvertently do something that breaks everything.

It appears that besides having support for newer TLS versions in the JDK, the JavaMail API might also need to support newer TLS, at least when STARTTLS is involved, which may not be the case in the 1.4 version of the API.