Hello, First: Sorry for my english, Second: the real problem, yesterday i setup an ubuntu 9.10 server with ISPConfig3, like in here: http://howtoforge.com/perfect-server-ubuntu-9.10-ispconfig-3-p3 After installation everything's good, I started setting up the domains what I handle. After I setup 2 domain I started testing: I was send a mail to [email protected], after this, I checked the virtualuser's mailbox and the mail was there. In the next step I send a mail to [email protected] this is my mailbox, and the gmail gives me an error message after sending, that's contains the following lines: 'This is the mail system at host mydomain.com. I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below. For further assistance, please send mail to postmaster. If you do so, please include this problem report. You can delete your own text from the attached returned message. The mail system <[email protected] Final-Recipient: rfc822; [email protected] Original-Recipient: rfc822;[email protected] Action: failed Status: 5.1.1 Diagnostic-Code: X-Postfix; unknown user: "admin"' I think postfix wanna send this E-Mail to a localuser called admin, but I have only vitrualusers, i don't know how I can fix this problem . My access to ISPConfig panel is mydomain.com:8080. I welcome any idea! Thanks a lot.