Are you using Outlook for Windows (the Windows Store UWP app for Windows 10 or 11) - the free online version (same layout as the UWP app) or the MS Office desktop version (2016, 2019, 2021 or 365)?
If it's the desktop version, open MS Word, then go to File, Options, go to the Proofing category, and check your settings as follows... (all the MS Office desktop apps share a common spell-check feature, so the settings you change in MS Word will also apply to ALL of them)
If you are using the Outlook for Windows UWP app (or the online version), open a blank email, click on the Options tab, then click on the Editor icon to display the drop-down menu, then select 'Editor Settings', and change the settings as shown below, then click OK to accept the changes.
You can also click on the 'Autoformat options' icon and check your settings there as well...
I hope this helps you out...
