We use Postmarkapp for sending transactional emails, e.g. "click here to confirm your account" and I love that they keep a full copy of every email for 30 days. Not only can we inspect the response of the target mail server, timings, bounces etc but the full HTML raw and rendered.

https://railsautoscale.com/ for Heroku. It's more piece of mind when we get crawled or hit by an unbehaving security scan.