Rated 2 out of 5 stars

Installs fine.
Alert appears when emails are in Outbox
However, actual features are available to schedule the sends, no toolbar button etc

This review is for a previous version of the add-on (8.9.4). 

I don't quite understand what problem you're running into, but it would be really helpful if you submit a bug report through any of the methods described here: https://extended-thunder.github.io/send-later/#getting-help