1. I followed http://www.falkotimme.com/howtos/perfect_setup_fedora_core_4/index.php. And I doubt that whether information when postfix SMTP is authenticating is encrypted or not? 2. Can I follow Postfix-SMTP-AUTH-TLS-HOWTO instead of above URL in only installing postfix section? 3. 250-XVERP means? ( it is the difference between setup at Postfix-SMTP-AUTH-TLS-HOWTO and The Perfect Setup - Fedora Core 4 ) 4. I already completed ISPConfig installation, can I do adding smtpd_sender_restrictions = permit_mynetworks, reject_sender_login_mismatch smtpd_sender_login_maps = hash:/usr/local/etc/postfix/sender_login_maps to main.cf ??? 5. Every time I restart server, do I have to start some services? or leave the machine as it is. Thank you very much.