Some email programs, such as Microsoft Outlook, include a spelling checker. outlook_on_the_web_for_business relies on your web browser to check spelling. That’s why you don’t see a spelling checker button or spelling settings in JustOutlook.
Spell checking is available in Internet Explorer 10 and later versions, and current versions of Firefox, Chrome, and Safari. Check the options for your web browser to learn more about how to use it to check spelling.
To learn more about the browsers that are compatible with Outlook, see Supported browsers for Outlook Web App.