There was a lot of activity in this space when Mandrill "died" last year.

This comparison was a very good overview of hosted options: https://www.metachris.com/2016/03/free-transactional-email-s... | https://news.ycombinator.com/item?id=11328631

And the discussion there linked this detailed sheet: https://docs.google.com/spreadsheets/d/1Nb1YqYJq9eWm6ojLDRXd... | https://sendyhost.com/mandrill-alternatives-245/