A rock-solid setup for sending SMTP mail from your EC2 web server ➜ Paul Dowman. (None of this is EC2-centric, but it's particularly needed on EC2.)
A frequent topic of discussion on the EC2 forums is how to send email reliably, efficiently, and especially without it being marked as spam. I found that even with a valid SPF record most mail sent from an EC2 instance was marked as spam or silently discarded. This is probably partly because of the lack of matching reverse DNS records. Ubuntu 10.04 LTS (Lucid Lynx) The Ubuntu Cloud image can be run on your personal Ubuntu Cloud, or modified, rebundled and uploaded to Amazon EC2.
For further instruction on setting up a personal Ubuntu Cloud, see Getting Started with Ubuntu Cloud There are two images available, each for a different type of computer: 32-bit Cloud image For almost all PCs. EC2 and Ubuntu.