The entire idea of "dumb pipe" or "commodity" needs to go away. There is a reason why companies like Asana, Desk, and Minecraft chose Postmark, since their email is critical to their business and choosing the right providers makes a real difference. Now, if your emails are not critical, I can see how any service might work. I have yet to come across a product owner who is comfortable letting their customers wait for their transactional emails though - no matter the size of product or company.
Full disclosure, I'm the founder of Postmark - the best "dumb pipe commodity" money can buy.
