Configuring Postfix to do smtp/relay

# aptitude install postfix sasl2-bin

  Edit /etc/postfix/main.cf

#
# Transport com relay autenticado
#

smtp_sasl_auth_enable = yes
smtp_sasl_security_options =  noanonymous
smtp_sasl_password_maps = hash:/etc/postfix/saslpass

Edit /etc/postfix/saslpass

smtp.servername userlogin:password

Then, run:

  # postmap /etc/postfix/saslpass
# postfix reload

References

http://www.postfix.org/

Configurando o Postfix pra fazer smtp/relay autenticado