Calendar reminders in Outlook can't be dismissed or keep reappearing

Symptoms

When you try to dismiss calendar reminders in Microsoft Outlook, you discover that they can't be dismissed or keep reappearing.

Cause

The reminders folder or the reminder view is corrupted. A sync conflict may also prevent Outlook from dismissing a reminder.

Resolution 1

Delete the item using a command line:

  1. Close Outlook.

  2. Right-click the Start button in Windows and select Run.

  3. In the Run window, type or paste the command below and select Enter.

    outlook.exe /cleanreminders
    

If that method doesn't work, use Resolution 2.

Resolution 2

Delete the Reminders folder by using the Microsoft Exchange Server MAPI Editor (MFCMAPI). To do this, follow these steps:

  1. Download MFCMAPI from github (scroll down and then click Latest release).

  2. Exit Outlook.

  3. Open MFCMAPI.

  4. On the Tools menu, click Options, select both of the following check boxes (if they're not already selected), and then click OK:

    • Use the MDB_ONLINE flag when calling OpenMsgStore
    • Use the MAPI_NO_CACHE flag when calling OpenEntry
  5. Click Session, click Logon, select the profile that you want to change, and then click OK.

  6. Double-click the mailbox store that you want to open.

  7. Expand Root Container.

  8. Right-click the Reminders folder, and then click Delete folder.

    Note

    Do not delete the individual items inside the Reminders folder. The Reminders folder is just a view of upcoming events on the calendar. If the items inside the folder are deleted, those items will be removed from the calendar.

  9. Run the Outlook.exe /cleanreminders or Outlook.exe /ResetFolders command line. (This step re-creates the Reminders folder and adds any valid entries back in.)

Resolution 3

The sync issue can be fixed by clearing all offline items from the Calendar folder. This will remove all items from the local copy, but they can be downloaded again from the server.

  1. Right-click the affected calendar and select Properties > Clear Offline Items > OK. All items on the calendar will be removed.
  2. Select Send / Receive > Update Folder in the ribbon to force the items' download.