Grammarly is a grammar checking tool that can be installed in MS Word and Outlook, as well as major browsers like Chrome, Safari, Firefox, and Edge.
When compared to the grammar checking tools provided in MS Word, Grammarly is not only capable of identifying grammatical error, but it also provides with explanations, which can help you to learn and improve your grammar. Below is an example:
Errors caught by Grammarly:
You can make use of the free version of Grammarly if you wish to enjoy the grammar and spelling check features. There are additional features for its premium accounts version:
Please note that Grammarly does not offer an add-in for MS Outlook. However, you can download the Grammarly for Microsoft Word on your Mac. More details here.