@UtopiaOperaX I think that the batch size and throttle were designed to handle web servers that limit the number of emails that can be sent, such as 1000/hour.
Unless Amazon SES has imposed a quota (mine is 200 emails per 24 hour period but I am in a sandbox) then you don’t need to use batch processing.
You want to restrict the sending rate, so the throttle probably needs to be in the order of milliseconds if you want to get a rate near 20/s. Just adjust the throttle untll you are happy.