The first thing is to get Microsoft Outlook to use Microsoft Word as the default e-mail editor. The default e-mail editor could be configured to use WordPad, which doesn't perform the spelling and grammar verifications. To achieve this, please launch Microsoft Outlook and go to Tools, Options.
Once you have clicked on the Option button, a big box will popup. Then go to the Mail Format selection form and put a check mark on the "Use Microsoft Word to edit e-mail messages" box.
Click Apply and OK. Now, try to edit a new mail message like you always perform.
To prove the reliability of this computer tip, I have purposely typed a few mistakes in my e-mail to Mr. Bill Gates. The spelling mistakes will be highlighted as RED in color. The next step below shows how to correct these spelling mistakes if you have 398 in total inside your email.
Still on the opened e-mail, go to Tools, Spelling and Grammar or simply press F7 on the opened e-mail. The auto correct function will be launched.
The last step of verifying the e-mail is to activate the grammar check box as shown in the green circle below.