If you are an Insider using Windows 10 Mobile or Windows 10 for PC, you may want to check your Store for a late Friday update. Version 17.6224.42272 is now live, and it looks like an odd mashup of some small UI changes and the actual loss of a recent feature.
Comparing our two versions of the Outlook app and we noticed that the new Digital Signature and Encryption options have been removed from Settings. If we had to guess, there were some issues with the implementation and we'll likely see those security options come back in another build.
Full story from the WindowsCentral blog...