Rated 4 out of 5 stars

This looked pretty good at first, but the interface of the schedule dialog could be much clearer. Instead of "send to outbox" and "send now", it should only have a "schedule for send" button. I clicked the "send now" thinking that would send it as a schedule message. An email just went out Friday night instead of Monday morning... Why have a true "send now" button when you wouldn't even use this addon's functionality when sending a regular, non-scheduled email?

reply to @jikamens

Okay, that makes sense. Thanks!

This review is for a previous version of the add-on (4.4). 

I have tried various different layouts for the prompt window, and no matter what I do, somebody complains. At some point all that's left to do is to find the interface design that seems to provoke the fewest complaints, and do my best to document it for the few people who are still confused.

I'm not sure how to make it more obvious than it is now -- the "Put in Outbox" and "Send Now" buttons are in an entirely separate box in the dialog, outlined in red, and the button for scheduling a message is labeled "Send Later at time(s) specified above" -- without making the interface more clunky rather than less.

I understand that some people do not find the interface entirely intuitive. That is why there's a user guide as well as detailed, explanatory tooltips that pop up when you hover over the buttons.

The "Put in Outbox" and "Send Now" buttons are there because people use them. "Put in Outbox" is necessary because when Send Later is installed, that button is the only way to put a message into the Outbox. "Send Now" is necessary because some configure their "Send" button to _always_ pop up the Send Later dialog, and they need the option when the dialog pops up of sending the message now rather than scheduling it for later.