Rated 1 out of 5 stars

Complete waste of time for my purposes. I have spent almost two days trying to accomplish one simple task, or at least,one task that sounded simple when I started trying to figure out how to do it twowhole days ago: When a new email comes in, I want a notification with the subject line. Mozilla helpfully deleted this ability from the Mac version a while ago, and everybody everywhere says "Use Filtaquilla! Use Filtaquilla!" Well, if Filtaquilla ever provided some way to do this, the documentation doesn't exist anymore, and every single thing I tried (from launching a shell script to running an applescript command to using a javascript alert) either had documentation that was flat-out wrong, documentation that simple didn't exist, documentation that consisted of nothing but a broken link, etc. This has been a huge, frustrating waste of my time and I wish I had never heard of this add-on. There is no point to developing a complicated addon if it is not possible to find documentation for how to get it to work right!

I could have spent much less time simple finding another email client, one which will actually tell me WHAT EMAILS ARE ARRIVING.

This review is for a previous version of the add-on (3.1). 

This sounds like a feature request - why don't you raise an issue on the github:
https://github.com/RealRaven2000/FiltaQuilla/issues
Just push the [New Issue] button and I can help you deal with it. Remember the review tool isn't really a good place to help you. Note that the notifications at the moment are done by Thunderbird, but a new "custom notification" action might add some value for other users as well. It's actually much harder to suppress the built in notification than adding new ones.