Is the email from your amazon ec2 web server bouncing back to you with an error like the following?
Remote host said: 550 5.7.1 <user@example.com>... Mail from x.x.x.x blocked using Trend Micro oRBL+. Please see MAPS - Support - Lookup Tool Giving up on x.x.x.x
When that has been completed wait a couple days and then request to be delisted from the Trend Micro RBL using the link from the original bounce message.