Use the following article to configure Outlook to always check spelling before sending an email.
1. Open Outlook and click File.
2. Click Options from the File menu.
3. From the Oultook Options windows, (1) select Mail from the menu pane. (2) Check the box for Always check spelling before sending. (3) Click OK to save the changes.
Note: You can customize spell checking by clicking Spelling and Autocorrect from the Outlook Options window.
Spell check will now run for every email that you send!