Autocorrect won't stop correcting in Mail, even though it's off.

Hello, in Mail I have Autocorrect switched off. It worked OK for a couple of weeks but suddenly today it's started correcting again even though it's switched off. Toggling it on and off and restarting Mail does nothing, it just keeps on correcting.

I need to switch it off and keep it off, it totally messes up my productivity.

Any ideas?

This is on a Mac Studio running Ventura.