New Outlook Office 365 "Spell Check On Send"

That what I suspected, but I wanted to be sure before delivering the bad news. You are SOL.

Always Spell Check Before Sending - New Outlook
https://answers.microsoft.com/en-us/outlook_com/forum/all/always-spell-check-before-sending-new-outlook/df0aba2c-b452-4f24-8aaf-ed4a7d64938d

"Currently, this option is not available in New Outlook."

Thanks for the link, but I think you're confusing the issue. The spell check works and highlights misspelt words with normal red wiggly underline, but when you hit send it just ignores the fact that there are misspelt words and sends the email anyway. In the legacy / old outlook , it would bring up the spell check window and not send until the spelling check has been completed / cancelled. That is the behaviour I want it to continue doing, but I can't see a way to do it.

Unfortunately not - the instructions for "new outlook" are correct and working as designed, but does not force a full spell check before sending, which is a feature in "normal" outlook, as detailed in the instructions for "Classic Outlook".

This is a feature that is missing in "new outlook" that they need to bring back. How do we request that?

The only other thing I can think of is your Privacy and Data settings. See:

https://www.reddit.com/r/Outlook/comments/1dnldos/new_outlook_update_no_spell_check/

Does this Microsoft Support article apply to your situation?

https://support.microsoft.com/en-us/office/check-spelling-before-sending-a-message-620b24fc-9cc5-4a2f-a26b-9ff4e02cc193#:~:text=%E2%80%94you%20can%20set%20Outlook%20to%20check%20spelling,the%20Always%20check%20spelling%20before%20sending%20box.