Have you enabled both spell checkers in your email? These tools will carry across many of the Chrome sites you use making them very helpful.
Open a new email message.
Right click any place you would start typing some text.
Select Check the spelling of the text fields.
Repeat the process and click Ask Google for suggestions.
If you repeat the right click process you should see a check by the two spell check options.
If you misspell a word just right click on it.
At the top of the popup you will see suggested spellings. Click the word to replace the misspelled word.