Office 365 tenants can use Exchange transport rules to apply autosignatures to outbound email, including messages protected with encryption. You can even include some properties of the sender extracted from Azure Active Directory, and you can add an exception so that the autosignature isn’t applied to replies.
Office 365 offers different ways to apply encryption to important messages. When those messages hold sensitive data known to Office 365, like credit cards or passport numbers, we can define a transport rule or DLP policy to protect outbound email automatically. And while you can define rules and policies through the GUI, PowerShell is available too.