The spellchecker will spell check each incorrect word by highlighting the word and displaying a list of words that you can replace the word with. You can spell check your messages before sending them, by doing the following:
Click the Spellchecker button in the Compose Mail window.
The Spellchecker will display a dialog box with a list of replacement words for you to select from. Select a replacement word and click the Replace button.
If the word is correct you can click the Ignore button and the spellchecker will move on to the next incorrectly spelt word.
Once spellchecker has checked the entire message, click the OK button to close the spellchecker.
Note:
You can automatically spell check each message before you send it by activating the Perform spell check before mail is sent option in the Mail Preferences dialog box.