Rated 3 out of 5 stars

Works very well (even in HTML mode) but, as another user reported, it also highlight empty recipient lines which impedes the goal of the addon: as you always see an highlighted field, it doesn't catch you eyes anymore.
Please fix this detail and it'll be perfect :-)

Rated 4 out of 5 stars

First of all, thanks for this extension. I have been looking for something like that for quite some time.

The main issue is that it only works for plain text messages right now (version 1.03). If I compose an html message, I do not get the address highlighting.

Also, (in plain text obviously) the highlighting happens even when the recipient line is still empty or unfinished. This is a little bit annoying. Having the highlighting happen only on completed recipient lines would make it even better.