Using older versions of Outlook for Mac for personal email and calendar
For Mac users: Switching to legacy Outlook solves the problem, or switching to Beta (I am a Mac user) can help. You can switch to Beta by using the steps here - Help menu > Check for updates > Advanced > Change the channel option to Beta > Check and get the available updates. However, you must ensure you have installed Office from Microsoft, not App Store. If you are not sure just uninstall and install again from your portal. You can download Office from your portal here. - https://portal.office.com/account/?ref=MeControl