The TLS Overview Report displays the TLS encryption that's used for the connection when messages are delivered to and from your Office 365 organization. The connections that are established with other email services are encrypted by TLS when TLS is offered by both sides. You can find out more about how we use TLS to protect your messages in transit here.
By default, the report offers a snapshot of the last week of mail flow. You can select Filter and change the date range up to 30 days. The breakdown of TLS versions shows you the level of protection that's used for your messages. Currently, TLS 1.2 is the most secure version of TLS that's offered by Office 365.
The Report view shows the percentage breakdown by TLS version. You can view the mail volume behind those percentages by selecting the slice of the chart or by navigating to the Details table view.
Often, you'll need to know the TLS encryption that's being used for compliance audits. You probably don't have a direct relationship with most of the source and destination email servers (you don't own them, and neither does Microsoft), so you can't really take action to change the TLS encryption based on this information.
But, you can use connectors to ensure the best available TLS protection for messages that are sent between your email servers and Office 365. Mail flow between Office 365 your own email servers or servers that belong to your partners is often more important and sensitive than regular messages, so you'll want to apply extra security and vigilance to those messages. You can upgrade or fix your own email servers to improve the TLS encryption that's being used, or reach out to your partners to do the same. The Connector Report displays both mail flow volume and TLS encryption for messages that use your Office 365 connectors. For more information, see Connector Report.