I have an Ubuntu12.04 server running on Amazon AWS, and have a domain purchased from godaddy.com I have setup a mail server with Postfix and Dovecot. I am able to recieve most mails from senders. But some users are not able send mails to my domain. Almost all of these users who are not able to send mails are users with firstname.lastname@example.org accounts. However, many other Gmail users are able to send mails, including me. Also, when a sender is not able to send the mail, he/she doesn't recieve a bounce and nothing is logged in mail.log for that email address
I am really lost as to what the problem may be. My guess is that the domain name is not configured properly. I have pointed MX and CNAME to @. @ is pointing to my server IP address.