Limit amount of emails sent per time frame?
There is an option, Queue mail module that queues all output emails in the queue ( you can define what email Ids queue). then set Cron to run each hour with ultimate_cron module)
the only problem is that you can not define how many hours can be sent in a Cron run. you can just set how many seconds the Cron can be run ( Queue processing time) . I think with a couple of tries you find your desire time.