How do you send mails from Amazon EC2?
papyromancer: I remember having a problem with this when I set up an ec2 instance.  I don't have any links handy (it was over a year ago), but I remember getting some helpful responses from gmail when my server attempted to send mail to their users.  Something about being Greylisted or maybe I'm remembering that it came through in my postgrey logs.The best I can remember for my solution was to get an elastic ip, then fill out some forms with a watchlist organization, and add some fancy txt records to my dns.A couple days later emails were going out fine.Sorry I can't be more specific, but it was one of those things that hat me beating my head against a wall for a few days, and after a few days of the steep learning curve for sending email the number of things I tried vastly exceeded the number of things that worked, so my notes are of little help.