@mormerod -- have you tried these instructions: How To: Use Shaw Internet services with Microsoft products
There should be only tiny differences between Outlook 2016, Outlook 2019, and Outlook 2021. After that many years, one hopes that they don't need any changes between versions.
Thank you so much - we have been struggling with this for several years now. Followed your step by step and all my husband's emails are showing up now. Thanks for taking the time to walk us through it step by step!