To mitigate Outlook 2016 for Mac stability issues, users should keep their Mac operating system software and Outlook software up to date.
How do I update my macOS software?
To update your Mac operating system software, follow the instructions found on the Apple support website: https://support.apple.com/en-us/HT201475 or through your company’s standard software distribution process.
How do I know if my software is out of date?
In Outlook for Mac:
Go to the Help menu and click Check for Updates to launch the Microsoft AutoUpdate tool.
Install the available updates.
You can also get the latest update from our monthly release notes.
Office 365 is designed to work best with Office 2016 for Mac.
What if my Office 2016 for Mac applications continue to crash?
There is a known issue with Apple’s macOS 10.13 and Office 2016 for Mac applications specific to proxy networks and Outlook for Mac. Contact your local network administrator for more information about your network settings and go here for a possible workaround.