Hi,
Email security plugin 7.5.1 was known to be compatible with Windows 10 and Outlook 2016 64 bit as per older notes.
However, I would recommend using the latest version of plugin available 7.6 to ensure you do not run into any issues during installation and older defects have been fixed.
Current compatibility matrix
https://www.cisco.com/c/dam/en/us/td/docs/security/email_encryption/Compatibility_Matrix/Cisco_Email_Encryption_Compatibility_Matrix.pdf
- Libin V