I have a scenario where we send excel files to external companies, because of the content of the files they need to be encrypted. My users use Outlook on the web, create the message and attach the excel workbook then choose encrypt in the options tab. The external company is not using O365 just excel. When they go to open the excel file, they get an error that says "You do not have credentials that allow you to open this workbook. You must request updated permissions from ***."
As the external company needs to open the file and we trust them how do I turn this off? There is no setting in the file itself (if I go to permissions "Restrict permission to this workbook" is unchecked.
There has to be something with the encrypt in Outlook on the web that is doing this but I can't figure out what.