Configure Postfix to Use Gmail SMTP on Ubuntu

Relaying Postfix mails via smtp.gmail.com:

First, install all necessary packages:

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

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

Open Configuration File

vim /etc/postfix/main.cf

Look for the Configuration and change the line as below

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 emailid@gmail.com:password

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

Finally, reload postfix config for changes to take effect:

sudo /etc/init.d/postfix reload

Now sent the Email to test

Check if mails are sent via Gmail SMTP server

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

echo "Postfix Test by Amjid Ali" | mail -s "Test Ubutu PostFix Amjid" amjid@syncbricks.com

Thank You. Please dont’ forget to comment.