Issue
Below is a reproduction of the dialog box from both Windows and Mac versions of Outlook:
Cause
If you see this dialog box, it is likely because there was a temporary communication issue on Microsoft's end. This is usually nothing to worry about; the dialog is asking you to verify that it's okay for your Outlook client to pull correct connection data from the mail server. Despite the ominous-sounding warning, this is a benign event and can be dealt with by simply approving the request.
Resolution
To resolve this issue:
- Check Don't ask me about this website again or Always use my response for this server.
- Click the Allow button.