Rated 5 out of 5 stars

@Motovt
Same situation for me.

Nov. 13, 2013: Yahoo! Mail Notifier 1.0.7 didn't work it.

This review is for a previous version of the add-on (1.0.5.1-signed.1-signed).  This user has other reviews of this add-on.

Yahoo changed things so the add-on won't work. I'm working on fixing this.