I feel like an idiot posting this, because, after all the posts about mail problems I've read, I can't seem to find the answer to this problem in any of those. I'm running Fedora Core 4 and Postfix. I've set up 3 domains with 2 users each (1 admin user and 1 'normal' user). Everything seems to be setup right, and working... the DNS is resolving correctly, all the web pages are displayed correctly, I even installed UebiMiau for a web interface, and I can log into that with all the users. The problem is that I send mail to, say hotmail/gmail email addresses, and I send email from hotmail/gmail addresses to users on the server, and the emails just seem to disappear. After I click send, I get a message that says, "Email has been sent" but I never see any email again. I have gotten 1 email back from hotmail saying: (I guess I'm expecting a lot more of those as they time out and send that message again and again until if fails or something) So, it wasn't failed... it just hasn't been delivered. Weird. I tried to find some log files of any kind of activity, but I have no idea where log files would be to look for them. Sorry I'm inept. Can anyone help me? Thanks.