My ISP requires SMTP authentication before one can send email. I have reconfigured several instances of Postfix to use this method and am going to document the necessary changes here for my reference.
add the following two lines to /etc/postfix/main.cf
smtp_sasl_auth_enable = yes smtp_sasl_password_maps = hash:/etc/postfix/smtp_auth
add the following lines to /etc/postfix/transport (replace “smtpauth.centurytel.net” with your ISPs smtp server)
localhost local: * smtp:smtpauth.centurytel.net:25
run “postmap /etc/postfix/transport”
add the following line to /etc/postfix/smtp_auth (replace USERNAME and PASSWORD with appropriate values)
smtpauth.centurytel.net USERNAME:PASSWORD
run “postmap /etc/postfix/smtp_auth”
run “postfix reload”