I'd been using Savard's Checker Plus for years with another browser. I'm glad to see it works just as well on Firefox. :)

This is good!

I extremely like this addon! Excellent!

Me ha encantado,le doy 5 estrellas

The app is very simple and useful. Kudos man. The only issue I'm facing is that the open in gmail option hasn't been working since the new gmail display update.