Outlook freezes with 'not responding' every morning

The big mailbox is the clue. Overnight the server collects a day of mail and Outlook syncs it all at launch while the antivirus scans the OST at the same time. Easiest win is File > Account Settings, double click the account, and pull the Mail to keep offline slider down to a year. Then test with Outlook in safe mode (hold ctrl while opening) for a week, if the hangs stop it's an add-in. A new profile is third, not first. Also empty Deleted Items and archive the old stuff, the file size genuinely matters here.