Greetings, I hope you are well. I have a Ubuntu server – installed utilized the PERFECT SERVER GUIDE guide - http://www.howtoforge.com/the-perfe...bind-mysql-php-postfix-dovecot-and-ispconfig3 There is an obvious flaw with the setup of POSTFIX and ISPCONFIG3. I have set up the server utilizing the EXACT instructions and settings as prescribed in the guide. The server will not accept external emails; from YAHOO, GMAIL, etc. 550 5.1.1 RECIPIENT NOT FOUND error is given when attempting to send external mail to the server. I have created email domains and mailboxes, via the ISPCONFIG3 control panel, and set all the DNS Records via the panel also. Everything is correct. I can send emails to external email sources (via SQUIRRELMAIL, ROUNDCUBE & SHELL), and local hosted sites but cannot receive return mail. My POSTFIX main and master file configurations are EXACTLY as in the guide so no need to post the contents of both here in the forum. My server is server1.example.com. I believe it may have to do with the virtual domains created with ISPCONFIG3 not being recognized by the external mail programs (GMAIL, YAHOO, etc.). I have scoured the internet and it appears this problem of not receiving mail is a common one, however, none of the solutions have worked for me. How do I fix please? I have websites that I am hosting that cannot receive external mail. I need to fix this as soon as possible please. Thank you kindly.