I recently stood up a couple of ColdFusion servers on Amazon's EC2. One of the servers is a staging server and I used localhost to send out mail. Turns out Amazon limits the amount of outgoing mail over port 25. Of course, Amazon offers a solution in the form of Amazon Simple Email Service (SES). http://aws.amazon.com/ses/ From the Amazon SES page:
Amazon Simple Email Service (Amazon SES) is a highly scalable and cost-effective bulk and transactional email-sending service for businesses and developers.
I signed up for SES, and within 24 hours was accepted with an initial outgoing limit of 10,000 emails per 24/hrs. Not bad. And as you prove your worthiness (i.e. no spamming), Amazon ups the limit.