I'm using Amazon EC2 to host a web server, but Amazon EC2's IP address space is blocked by Trend Micro MAPS DUL (http://securecloud.com/help/en/about_the_dul.html). Given that sending emails from a web server is often necessary, I need a way to send emails from the web server. I was using the Google Apps SMTP server for this until our website had enough users that we passed the Google Apps daily email limit. So now I'm looking for an alternative way to send emails. I'm sure many other YC News readers have encountered this... any suggestions?
Clarification: I don't mean email marketing services like ConstantContact.com but rather mail servers that can be used directly from our web server to send email notifications.