Does Secure Exchanges work with the web version of Outlook or only with the desktop application?

Does Secure Exchanges work with the web version of Outlook or only with the desktop application?

Yes, Secure Exchanges works in both the web version of Outlook and the desktop application (Outlook Classic or Outlook New). The difference lies in how you activate the application.

You can follow the steps outlined in this article to deploy Secure Exchanges on Outlook Web or Outlook New: How to install and activate Secure Exchanges on Outlook Web?