Do either of the following:
Check spelling
now in the item that's currently open
For Help on an option, click the question mark ,
and then click the option.
Note If Microsoft Word is your e-mail editor, see Word Help for ways to Check spelling and grammar.
Automatically check spelling when sending any item
From the main Microsoft Outlook window, on the Tools menu, click Options, and then click the Spelling tab.
Select the Always check spelling before sending check box.
Note Any words you add during a spelling check are placed in the custom dictionary, called Custom.dic.