If you are sending mass email I think you will love this -
While looking at Amazon SES ( which you can actually currently use with e-newsletter), I have stumbled across this excellent addition from the makers of Mailchimp.
12,000 free emails or notifications per month.
It's not a cheap as Amazon but you can very easily set this up to send from e- newsletter (smtp tab) and with a plugin and api for all other mail eg post notifications.
I am not in any way affiliated. I was just so elated to have found this I had to share.