Synchronization between applications is important as it helps to know the items are available in both the applications. If synchronization stops then the items are not updated and it creates problems. Synchronization problem in Outlook.com and Outlook desktop application create issues and does not update the data files. Many users complain that Outlook.com is not synchronizing with Outlook.
When synchronization stops the Exchange Active Sync (EAS) account type will no longer be available for Outlook.com. So, any appointments, contacts, tasks, notes will support syncing when the Outlook sync stopped working. So, it is very important to synchronize Outlook.com to Outlook 2016, 2013 and other versions.
So, the first step to remove the account from Outlook and use auto account setup to reconnect the account as Microsoft Exchange Account. Synchronize the Outlook.com to Outlook and then compare the calendars, tasks and other data in both accounts.
Add Alias to Outlook.com
Now the first step is to add the account as Alias to Outlook.com. Now add outlook.com alias to account first and then set it as the primary account.
Configuring MS Outlook
Remove EAS Account
The next step is to remove EAS account
Now the Outlook.com will sync with Outlook desktop app. In this way you can remove the Outlook.com sync issues.