Rated 1 out of 5 stars

The built-in dictionaries of Firefox and Thunderbird are not that good. Often the guesses it comes up with are hopelessly off target.
If you compare the spell checker of IESpell for example with Firefox you'll be amazed just how bad the Firefox one is.
The developers should examine IESpell and learn how to make a good spell checker.

This review is for a previous version of the add-on (1.19).