'Your connection is not secure' error in Outlook for Windows Problem When opening Outlook for Windows, the error of 'Your connection is not secure' appears. Environment Outlook for Windows Status 2023-10-27 – ITS is investigating and research a solution. Work-Around Click the 'Close' button. You may have to do this several times before Outlook is available to use. NOTE: Despite the error, it is safe to use Outlook for Windows at this time. There might be a delay of up to a minute opening Outlook Calendars where the certification error appears.