Chris, as a former Microsoft employee who worked as an editor on the Exchange team, I can see why your explanation is frustrating and confusing. Here are some issues:
- Someone who works on the team that's handling this change should reply to users' concerns in clear English, putting themselves in the users' shoes.
- In the email, which was forwarded to me by my sister, it's not at all clear what "third-party email and calendar apps" are being referred to. The customers are using some version of Outlook, so it makes sense that they would be confused at first, assuming things will be updated automatically.
- Is the issue that they can currently sign in to their Microsoft account using only their user name and password from the third-party product ? If so, the email needs to give some examples of third-party apps for context, then explain about Microsoft requiring more authentication to access Outlook, Hotmail, or Live.com and that updates need to be made.
- There need to be links to clear instructions for how to update without getting into the weeds. There should also be clear instructions about how to update Office 2021 (which they paid for, btw).
- And finally, the email says "Final Notice." Were earlier versions actually sent?