Usually a problem related to Word or Office
How to Fix Spell Check Not Working in Microsoft Outlook
I recently upgraded the version of Microsoft Office on my computer and discovered that my spell checker was no longer working! Normally it would automatically show me misspelled words right away if I mistyped them, but after the upgrade it no longer highlighted anything.
Even when I manually ran the spell checker, it would finish without marking or correcting the misspelled words! Annoying! After some research, I found a few possible solutions. You may encounter this problem in Word 2007, 2010, 2013, or 2016.
Because Outlook uses Microsoft Word for spell checking, you must first make sure that the spell checker in Word is working.
