On March 1, 2018, Microsoft will disable support for TLS 1.0 and TLS 1.1 protocols in many of its online services. That means TLS 1.2 or later version will be only allowed in browser-server and client-server connections. It is a good move and security enhancement. You should not even see this change unless you use the old legacy software.
During the past few weeks, I have been working on the project related to the implementation of the GDPR law for one of my customers. One of the milestone tasks was a migration to Office365 and Exchange Online. They were using external email service from one of the national providers so far. One of the applications they are still using is the on-premise CRM – I cannot name the product, but it has support from the vendor and every few months users get a new release. However, this CRM does not support TLS at all in deployed version, only the SSL, for connection to the SMTP server. It was not a problem for previous email service provider, but Microsoft is not going to enable SSL for you just because you need it.
Even in small company changing or upgrading the CRM is not a quick and easy task, so it was not an option in this case. So I had to make changes to SMTP service. My choice was to install SMTP Relay.