Install and Configure Postfix with Gmail SMTP for Perfect Mailing System

We can use Gmail SMTP to manage our outgoing emails and receive them in our inbox when properly configured with the Postfix program.

Generally, we will need a robust mailing system to communicate emails from our domain server. This internal emailing system helps us receive notifications about the server’s health and forward the incoming emails sent to the domain address.

In the following article, we will install and configure the Postfix program to SEND-Only using an SMTP server. Google Mail or Gmail supports using their SMTP server settings on non-Google apps. We will be using the same in the below article to configure the postfix program.

Just in-case if you are following us, this is our fourth article and video demo under the #CloudServer Series. We previously published how to set up a powerful LEMP Stack on the Ubuntu cloud.

Let’s get started with configuring Postfix as SEND-Only SMTP on the Ubuntu cloud —

What is Postfix?

Postfix is a free and open-source mail transfer agent(MTA) that routes and delivers electronic mail. It is released under the IBM Public License 1.0, a free software license.

It means you can download and distribute the software program freely. It’s one of the oldest and most used MTA software and an alternative to the Sendmail program.

Postfix runs basically on the Unix system, including our Ubuntu Cloud server. I use Postfix and recommend the same due to its simple configuration and setup.

Changing the Hostname on Ubuntu Server

Before we configure Postfix MTA, let’s adjust our hostname to reflect the correct domain name in our outgoing internal email.

Setting up a hostname is crucial if you’re using a custom domain for emailing. The hostname helps in proper mailing address.

One of the most accessible and reliable solutions I recommend is using G Suite to have a business email address, for example: [email protected]. You can also get a 20% discount on signing up using this Google Workspace coupon code.

About Hostname, you can check your current hostname using the below command line in SSH:

hostname -f

We can also use the hostname command to change the Ubuntu Server hostname.

hostname example.com

I will be changing the hostname to demo.restorebin.com using below command.

hostname demo.restorebin.com

But, this hostname will be valid only until restart; however, to make this change permanent, edit the hostname and hosts file via SSH.

sudo nano /etc/hostname

Modify the hostname file to reflect below

demo.restorebin.com

Close the nano editor using Ctrl+c on the keyboard and save the changes. Next, modify the hosts files as well using nano editor:

sudo nano /etc/hosts

Modify line with IP Address 127.0.1.1 to reflect below:

127.0.1.1 demo.restorebin.com

Close the nano editor, and reboot the Ubuntu server using the below command:

reboot

Note: make sure you’re using your domain name and address; the demo.restorebin.com is just for example.

That’s it! You have successfully changed the hostname of the cloud server.

Installing Postfix on Ubuntu Cloud

Get started with the install and configure Postfix by updating the apt repository first using the below command:

sudo apt-get update

Run the below command to install Postfix and other mail utilities on the Ubuntu cloud.

sudo apt-get install mailutils

You will be prompted to provide additional information and configure Postfix during installation. First, it will ask to select the best suitable server settings. Since we are going to use SMTP, select the Internet option from the list and hit the [Enter] button.

Next, you will be asked to set the fully qualified domain name FQDN. This is nothing but the domain extension that you want to receive the email from.

We should generally set this same as hostname. Hence, fill in the same and hit the [Enter] button. In my case, the hostname is:

demo.restorebin.com

You can always reconfigure the Postfix using the below dpkg command:

dpkg-reconfigure postfix

Configure Postfix with Gmail SMTP

Now that your Postfix is installed, head over to configure Postfix to use Gmail for SMTP relay.

Open the Postfix configuration file main.cf using located in /etc/postfix/ directory.

sudo nano /etc/postfix/main.cf

Please scroll to the bottom to find the relayhost = option and set it to the Gmail SMTP server

relayhost = [smtp.gmail.com]:587

We will be using the encrypted TLS connection for all the outgoing emails; hence the port number is set to 587

Next, we will be adding a few lines at the end of all other existing code to enable secure authentication and read the hashed password for SMTP.

# Enables SASL authentication for postfix
smtp_sasl_auth_enable = yes
# Disallow methods that allow anonymous authentication
smtp_sasl_security_options = noanonymous
# Location of sasl_passwd we saved
smtp_sasl_password_maps = hash:/etc/postfix/sasl/sasl_passwd
# Enable STARTTLS encryption for SMTP
smtp_tls_security_level = encrypt
# Location of CA certificates for TLS
smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt

Also, ensure that the myhostname = value is set to the hostname we defined earlier. In my case, I’ll be setting it to:

myhostname = demo.restorebin.com

The last thing you need to change in Postfix’s main configuration files is adjusting the mydestination value. Edit the value to reflect something similar to this.

mydestination = localhost.yourhostname.com, , localhost

You can now close the editor and save the changes.

Next, we will add the password credentials into sasl_password for authenticating the encrypted SMTP connection.

First, create a new file using nano editor:

sudo nano /etc/postfix/sasl/sasl_passwd

Add the Gmail password in below format in sasl_passwd file:

[smtp.gmail.com]:587 your-email-address@gmail.com:password

Replace with your Gmail address and password in the above code before pasting into sasl_passwd file.

Convert the sasl_passwd file into a database file, and delete the original file from the server. We can use the postmap command for converting.

sudo postmap /etc/postfix/sasl/sasl_passwd

This will create a sasl_passwd.db file in the same location.

Change the security and ownership of the password file to restrict root user access and read-write only.

chown root:root /etc/postfix/sasl/sasl_passwd.db
chmod 600 /etc/postfix/sasl/sasl_passwd.db

Finally, restart the postfix using the below command to make the changes permanent.

sudo service postfix restart

At last, change the setting in Google Account to allow less secured non-Google apps to use authentication to send emails via SMTP on your behalf.

Sending a Test Email

Once you’ve restarted the Postfix post-configuration, try sending a test email using the below command.

echo "Test Postfix Gmail SMTP Relay via https://restorebin.com/?p=5809" | mail -s "Postfix Gmail SMTP Relay 1" your-email-address@gmail.com

Do not forget to replace the Email ID with your mailing address.

Changing the Full Display Name

When you received your test email, you might have noticed that the display name is root.

To change the display name, you need to define it using the chfn script. CHFN is nothing but an acronym for Change Full Name.

Let’s see what names the users have on our server using the below command.

getent passwd $USER | cut -d ':' -f 5 | cut -d ',' -f 1

This command will output all the Users’ full names. And since we have only a root user, we will watch the only following output.

root

Using the below command, you can change any Unix user’s display name or full name.

sudo chfn -f "FirstName LastName" username

For example, I will be changing the full name of root user to ‘restoreBin Demo,’ hence my command line will be:

sudo chfn -f "restoreBin Demo" root

That’s it; the user’s Full Name or Display Name has changed successfully.

Resend Test Mail

You’ve made the changes to Hostname and Display Name of the root Ubuntu user. Try sending an email again to check if the changes are applied using the same command.

echo "Test Postfix Gmail SMTP Relay post modification via https://restorebin.com/?p=5809" | mail -s "Postfix Gmail SMTP Relay 2" your-email-address@gmail.com

This will also help to validate whether the server is intact and not broken after changes.

Video on Postfix Configuration

Watch and learn to configure Postfix on Ubuntu Cloud Server with Gmail SMTP Server for internal emails.

I hope you liked the video; please subscribe to our channel.

What’s next in the #CloudServer series?

This article teaches about the emailing system and configuring Postfix on Cloud Server. In the following article, I will be sharing how to generate a free SSL certificate using Let’s Encrypt.

Let’s Encrypt is a free Open Source certificate generator powered by the community, which helps establish the secured connection between host and server. You might also want to know that HTTPS secured connection is a ranking factor in search engine optimization.