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-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
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
Note: If you run into issues with above command, try changing certificate name to thawte_Primary_Root_CA.pem in above command. Thanks Alexander Bakker for the note.
Finally, reload postfix config for changes to take effect:
sudo /etc/init.d/postfix reload
Testing
Check 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
To further verify, if mail sent from above command is actually sent via Gmail’s SMTP server, you can log into Gmail account USERNAME@gmail.com with PASSWORD and check “Sent Mail” folder in that Gmail account. By default, Gmail always keeps a copy of mail being sent through its web-interface as well as SMTP server. This logging is one strong reason that we often use Gmail when mail delivery is critical.
Once configured, all emails from your server will be sent via Gmail. This method will be useful if you have many sites on your server and want them all to send emails via Gmail’s SMTP server.
Alternatively, you can use a plugin like WP Mail SMTP so that mails from your particular WordPress site will be sent using Gmail’s SMTP server.
Please note that Gmail’s SMTP server has a limit of 500 emails per day. So use wisely! 🙂
Troubleshooting
Error: “SASL authentication failed; server smtp.gmail.com”
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