This tutorial will show you how to sync Webmail Calendar with Outlook 2016.
Without adding the email account itself to the Outlook Desktop Client Software, you can sync Webmail Calendars to multiple instances of Outlook.
Step 1: In Webmail, go into Calendar.
Step 2: From the Action menu, select Add to Outlook.
Step 3: Click OK.
Step 4: Click Open link.
Step 5: Click Advanced...
Step 6: Give this calendar a name, click OK.
Step 7: Click Yes.
Step 8: You will now see your Webmail Calendar folder.