Does the spellcheck work fine in Word? Also, when you're typing a new message, does the spellcheck work if you manually run the Spelling & Grammar checker?

I would first double-check and make sure that Check spelling as you type is enabled.

1. Click the File menu.
2. Click Options.
3. Click the Mail tab.
4. Click the Spelling and Autocorrect button.
5. Make sure that the option "Check spelling as you type" is checked.

-SW