How to Configure Postfix to Use Gmail SMTP on Ubuntu

Configure Postfix to Use Gmail SMTP on Ubuntu

If you want to use a Gmail account as a free SMTP server on your Ubuntu-Linux server, you will find this article useful. This guide is tested with Ubuntu 12.04. If you face any issue, feel free to use comments-section below.

Relaying Postfix mails via smtp.gmail.com:

First, install all necessary packages:

sudo apt-get install postfix mailutils libsasl2-2 ca-certificates libsasl2-mo

If you do not have postfix installed before, postfix configuration wizard will ask you some questions. Just select your server as Internet Site and for FQDN use something like mail.example.com

Then open your postfix config file:

vim /etc/postfix/main.cf

and following lines to it:

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

 You might have noticed that we haven’t specified our Gmail username and password in above lines. They will go into a different file. Open/Create

vim /etc/postfix/sasl_passwd

And add following line:

[smtp.gmail.com]:587 USERNAME@gmail.com:PASSWORD

If you want to use your Google App’s domain, please replace @gmail.com with your @domain.com

Fix permission and update postfix config to use sasl_passwd file:

#sudo chmod 400 /etc/postfix/sasl_passwd 

#sudo postmap /etc/postfix/sasl_passwd

Next, validate certificates to avoid running into error. Just run following command:

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

inally, reload postfix config for changes to take effect:

sudo /etc/init.d/postfix reload

Testing if mails are sent via Gmail SMTP server:

If you have configured everything correctly, following command should generate a test mail from your server to your mailbox.

echo "Test mail from postfix" | mail -s "Test Postfix" you@example.com