Rated 3 out of 5 stars

1. It does not offer sentence rephrase like Grammarly! Is however way more practical to use for the spellchecking as Grammarly!
2. If you opt in for premium, Thunderbird always starts with basic account until you login. Which is time consuming!
3. It does not work in all web forms, like in this one here for example.
4. I use Office 2016 on main PC and two laptops. On none of them LT plugin for Office 2016 is working, yet support claims it does work on their office 2016.

It feels like LT is still being in the development stage. But the hope for better days is also quickly gone, as one always get an support reply like: "It does work at our place", problem solved! For LT at least...

This review is for a previous version of the add-on (5.3.3). 

1. Rephrasing is available (for English) via the synonym feature. Activate the feature via "LT" in the toolbar, then double-click a word in a sentence.
2., 3., and 4. Sorry, I cannot reproduce this. Can you contact our support about this? You can find the email at https://languagetool.org/legal