aCalendar is not involved in calendar synchronization. The app is just an user interface to the Android calendar storage and does not save any calendar data itself.

You don't setup your Microsoft Exchange Account within aCalendar.

All Android devices offer native synchronization to MS Exchange. On many devices you can choose between Google's Exchange implementation and one from the phone manufacturer.

To sync any Microsoft cloud service or corporate Exchange calendar with Android, you can use Android's built-in Exchange sync. This is provided and updated through the Gmail app (hence the Gmail Icon for the account).

Also, many phone manufacturers (e.g. Samsung, Huawei) offer their own sync (usually called Active Sync or Enterprise) which may offer more features than Google's implementation. 

The MS Outlook app also offers sync to Android since October 2020, but it's still very buggy. Please make sure in the Outlook App settings that 'sync calendars' is switched on. (How do I sync my Outlook Calendar to the default Calendar app(s)?)

Recommended setup

  1. Go to your Android device settings / accounts. 
  2. There create a new account.
  3. Select 'Exchange' as account type, 
  4. then make sure to select manual configuration. You can ignore any warning to go back to select "Outlook, Hotmail and Live".
  5. Use as server for all MS cloud services.

Known Issues

Limitations of MS Exchange Sync in Android

  • Some device manufacturers have limited sync of past events, sometimes this is configurable in the account settings or Gmail app settings (coupled with the synchronization of past emails).
  • Android has no support for attachments in MS Exchange.
  • Android has no native support for the availability field out-of-office, but we are working on support for proprietary solutions if implemented by the phone manufacturer.

Issues with Samsung's Active Sync

  • Sync from Android to Outlook not working
    Samsung's Active Sync currently fails to sync any new or modified events that have a category stored. The newest version of the Samsung email app (which provides the Active Sync adapter) that still works is available e.g. on APK Mirror.
  • Exchange Calendar missing after restart on Samsung device in Ultra Power Saving Mode
    This is a Samsung firmware bug in all Android versions. Please open the Samsung email app, to re-grant Exchange admin-permissions and re-enable calendar sync in the Exchange account. We reported this bug in verbose detail to Samsung.

Issues with Google's Exchange Sync

  • Double or Triple entries in MS Exchange calendars
    Lately, several users reported duplicate entries, in their Exchange calendars. This can be solved by removing and re-adding the account in Android account settings. 
  • Calendars appear twice / deleted calendars are displayed
    Google's Exchange Sync seems to synchronize deleted calendars without the corresponding marking. Please deactivate this in the calendar list.
  • Shared calendars / sub-calendars are missing
    Google's Exchange Sync can only synchronize the main calendar for some account/server types.

Issues with Outlooks new Sync

  • Outlook only syncs the values free, busy and tentative, not away/elsewhere.
  • Outlook does not sync categories.
  • Outlook does not sync the private status.
  • All-day events are synced to Outlook one day too long.
  • MS messes with the description field which breaks aCalendar colors and contact linking.