This assumes you are running a recent version of MacOS.
If you have Mac Mail (aka Mail.app) connected to Exchange do the following:
click Mail - Preferences
click Accounts
click account corresponding to Canisius Exchange
click Server Settings
change User Name to canisius\username
uncheck Automatically manage connection settings
change https://exchange. to https://outlook. for both Internal and External URL
click Save
REBOOT!!!! This is needed to clear some background processes used by Mail that do not get their settings updated until a reboot is done.
