Rated 3 out of 5 stars

Used to work great, doing exactly what it claimed. However it is currently broken for TB 137. Hopefully there's an update soon, however I've not heard back from the developer.

This review is for a previous version of the add-on (1.3.6). 

We're working on the TB 137 support. I'm sorry that we didn't make it in time for the release. This is a new (and very challenging) process for us, so we're still learning how to deal with the monthly releases.

We're hoping to have the release ready in a few days.

UPDATE: We have Owl 1.3.7 for Thunderbird 137 ready. It's been reviewed and is online in TB addon store for updates.