There is an ongoing issue that occurs when attempting to use Microsoft Exchange in iCal and Mail applications with OS X Yosemite and OS X El Capitan. Both applications do not support Push at all, and instead only sync with an Exchange server in intervals.
If you are experiencing syncing issues with Microsoft Exchange with OS X, complete the steps below to try and resolve the issue.
Note: This is not a permanent solution, and does not guarantee that the problem will not appear again.
- Close iCal.
- Click the Apple icon in the menu bar and select System Preferences.
- Select Internet Accounts.
- Select Exchange account.
- Deselect Calendars.
- Close System Preferences.
- Hold down the Option key and select Go > Library.
- Navigate to the Calendar's directory and find the Calendar Cache file.
- Delete the cache file.
Note: iCal crashes initially because of the missing cache file. Just click OK and re-open the application.
- Wait as iCloud events are rebuilt and the back up process is completed.
Navigate back to System Preferences and turn on Exchange calendar again.
Note: Refer to steps 2-5 to do this.