I've tried SES. The implementation is the difference between making a call to SMTP and making an API call, which is quite trivial. The other thing to consider

I've tried SES. The implementation is the difference between making a call to SMTP and making an API call, which is quite trivial. The other thing to consider is deliverability from Amazon. I would hope that they run on a different IP range than EC2, but besides that they have a different risk profile than other SMTP hosts. Amazon is able to make it as cheap as they do because their risk is based on implementing quotas based on reputation in addition to making you verify the sender address (both making it quite difficult to use the service to send spam). So far that makes it pretty solid. The only thing I haven't been able to figure out so far is how to set DKIM keys.