I've Office 365 for enterprise (version 2008, build 13127.21216) on a HP Elitebook with Windows 10 (1909).
CTRL + left / right arrow shortcuts (for jumping one word) does not work in Outlook. When I press them, just nothing happens.
The issue is the same for both pressing the dedicated arrow keys, or pressing 4 / 6 when numlock is turned off.
Those work correctly in all other applications including Office (Excel, Word..) and also browsers, notepad++ ...
All others shortcuts working well also in Outlook, even CTRL + Shift + left / right.
The problem is so odd, that I'm not sure whether it's a driver issue, some other activities linked to that shortcut (I don't have any shortcut manager installed) or a bug in Outlook.