The recent problem Outlook users were having with e-mails turning up blank was due to an interaction with Word <https://www.theregister.com/2021/05/17/outlook_incident_report/>. Why Word? Because management of HTML-format mails in Outlook used to be the responsibility of (an embedded instance of) Internet Explorer, until that was abandoned because of all the security holes. So now Word handles that feature: For those who wonder why Outlook makes it so hard to format emails sensibly when doing things like quoting parts of an email received in the reply and typing in-line comments, or putting the background of the incoming email behind the reply: it is the interaction with Word that is to blame. Fair warning: ... today's Windows and Office 365 users are one bad update away from hours of lost productivity.