This document describes how to configure postfix to use gmail as relay server on debian squeeze.

1. Install the required package. On the dialog window please select No configuration.

apt-get install postfix libsasl2-2 ca-certificates libsasl2-modules

2. Configure postfix

vim /etc/postfix/main.cf

relayhost = [smtp.gmail.com]:587
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options = noanonymous
smtp_tls_CAfile = /etc/postfix/cacert.pem
smtp_use_tls = yes
alias_maps = hash:/etc/aliases
inet_interfaces = 127.0.0.1

:wq

3. Define an username and a password

vim /etc/postfix/sasl_passwd

[smtp.gmail.com]:587 email@gmail.com:password

:wq

4. Fix file permissions

chmod 400 /etc/postfix/sasl_passwd

5. Generate Postix lookup table

postmap /etc/postfix/sasl_passwd

6. Use the ca-certificate package we installed and tell it where it can validate the certificate

cat /etc/ssl/certs/Thawte_Premium_Server_CA.pem | tee -a /etc/postfix/cacert.pem

7. Restart postfix

/etc/init.d/postfix restart

8. Test installation

echo "Test from a postfix configured to use gmail as a relay server" | mail -s "Test from postfix" "email@example.com"