It is my understanding that ActiveSync is no longer supported by Microsoft. Therefore many email clients are ending support for ActiveSync. Since your Zimbra email server uses ActiveSync for syncing calendars and contacts, it seems to me that the CalDAV and CardDAV support in Zimbra should be turned on so that this service can continue. I have read elsewhere that Shaw hasn’t turned on that support feature in Zimbra.
Can you advise was the plans are to continue to support Calendar and Contacts syncing? A simple plan would be to just turn on this feature which is included in Zimbra.