There are known issues that cause some email clients, especially older clients and those on some mobile devices, to provide inconsistent and unreliable updating of calendar information via Exchange ActiveSync. An exact cause is not always known and can vary from client to client. However, to help work around these issues, the following is suggested:

  1. Make sure to use the most current version of your desktop client software, especially Office 2016 or 2019 (Windows), or 2016 or 2019 (Mac).
  2. Mobile devices are known to have issues with ActiveSync, especially those running older versions of their system software. For details, see the Microsoft article at http://support.microsoft.com/kb/2563324.
    • Update your phone/device software when prompted.
    • If you are using an older device, such as a first generation iPhone or iPod Touch, you will not be able to rely on the calendar and should consider an upgrade.
  3. Other suggestions for mobile device use:
    • Beware of dropped signals and poor coverage areas that could have an impact on your use of the calendar.
    • Consider managing your appointments only from Outlook or OWA.  Assuming reliable coverage, you might, for example, be able to create new appointments on a device, but may not want to invite, accept, or decline meetings, or modify any recurring events, until you are using Outlook or OWA (or have successfully tested these functions on your device). Additionally, Outlook for Windows and OWA have shown to be more reliable than Outlook for Mac.
  4. Manage recurring meetings carefully and only from OWA or a current version of your desktop client software, especially Office 2016 or 2019 (Windows), or 2016 or 2019 (Mac). Recurring meetings should not be created as indefinite and should be limited to the lowest number of occurrences possible.
  5. Ensure that Exchange is selected as your default calendar under Settings/Mail, Contacts, Calendars/Default Calendar: Calendar
  6. If maintenance of your calendar is delegated to an administrator, for best results follow these guidelines:
    • Keep calendar accepts and declines to only one user, preferably the administrator.
    • Keep calendar accepts/declines to only one system. Use a desktop or laptop as the sole device to accept/decline invitations. Do not use a mobile device to accept, decline or edit a calendar event when your calendar is delegated.
    • If it is not possible to limit the devices used to maintain a calendar, at a minimum ensure that all system types are the same (e.g. all delegates use the same, and latest, version of Windows and Outlook).