Microsoft 365 (Outlook on the web, Outlook for Windows) - How to spell check before sending emails in Outlook
Outlook on the web relies on your web browser for checking spelling. That's why you don't see a spell check button or spelling settings in Outlook on the web.
Microsoft 365 Outlook clients use the Microsoft Editor for enhanced spelling, grammar, and style suggestions before sending emails in new Outlook for Windows, classic Outlook for Microsoft 365, or Outlook on the Web. Editor provides real-time suggestions in the message body (underlined in red) and in the Editor window.
Learn more.