Postfix relayhost/transport with authentication

Example: Outbound SMTP with authentication
SMTP: smtp.somehost.com
Username: pank
Password: 8888

Edit /etc/postfix/sasl_passwd
smtp.somehost.com pank:8888

Edit main.cf, add
relayhost=smtp.somehost.com
smtp_sasl_auth_enable=yes
smtp_sasl_password_maps=hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options=noanonymous