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# How to configure Postfix to use Gmail SMTP on Ubuntu 18.04 & 16.04 | LeetDev

In this article we are going to configure Postfix to relay mail through Gmail’s SMTP server on Ubuntu 18.04 & 16.04. If you want to use a SMTP server other than Gmail, please see [How to configure Postfix to use an External SMTP Server](https://devanswers.co/postfix-external-smtp-server/).

## Prerequisites

If your Gmail account uses [2-Step Verification](https://devanswers.co/enable-2-step-verification-google-account/), you must [create an application specific password](https://devanswers.co/create-application-specific-password-gmail/).

If you’re **not** using 2-Step Verification, please ensure that your Gmail account is configured to [allow less secures apps](https://devanswers.co/allow-less-secure-apps-access-gmail-account/).

## 1. Install Postfix

If you’ve already installed Postfix, skip to step 2.

Let’s update the package database first.

```
sudo apt-get update
```

Install `mailutils`, which will automatically install Postfix.

```
sudo apt install -y mailutils
```

On the first Postfix configuration screen, select **OK** by pressing `TAB` and `ENTER`

![](https://devanswers.co/wp-content/uploads/2017/02/postfix-config1-1024x682.png)

Select **Internet Site** and press `ENTER`.

![](https://devanswers.co/wp-content/uploads/2017/02/postfix-config2-1-1024x683.png)

**System mail name** should be your domain name eg. `example.com`, press `ENTER`.

![](https://devanswers.co/wp-content/uploads/2017/02/postfix-config3-1024x682.png)

Package should now be installed.

## 2. Configure Postfix

Edit the Postfix configuration file.

```
sudo nano /etc/postfix/main.cf
```

Find the following line `relayhost =` about 6 lines up from the bottom of the file and delete it.

Add the following to the end of the file.

/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
```

Save file and exit. (Press `CTRL` + `X`, press `Y` and then press `ENTER`)

## 3. Create Password and DB Files

Create the `sasl_passwd` file which will store our credentials.

```
sudo nano /etc/postfix/sasl_passwd
```

Insert the following:

/etc/postfix/sasl\_passwd

```
[smtp.gmail.com]:587 [email protected]:password
```

Replace `username` and `password` with your own.

Save file and exit. (Press `CTRL` + `X`, press `Y` and then press `ENTER`)

Create a hash database file for Postfix with the `postmap` command.

```
sudo postmap /etc/postfix/sasl_passwd
```

There should now be a file called `sasl_passwd.db` in the `/etc/postfix/` directory.

For added security, we will only allow **root** user to read and write to `sasl_passwd` and `sasl_passwd.db`

```
sudo chown root:root /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db
```

```
sudo chmod 0600 /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db
```

## 4. Sign Certificate

Now we are going to create the certificate.

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

There should now be a certificate file called `cacert.pem` in `/etc/postfix`

## 5. Send a Test Mail

We’ll now send a test email message. Make sure to replace [`[email protected]`](https://devanswers.co/cdn-cgi/l/email-protection) with your own email address.

```
echo "Test Email message body" | mail -s "Email test subject" [email protected]
```

Don’t forget to check your spam folder.

If you still haven’t received any mail, check the mail error log.

```
sudo tail /var/log/mail.log
```

If the mail log is empty or doesn’t exist, try parsing the syslog. This will return the last 50 entries for postfix.

```
sudo tail -f -n 50 /var/log/syslog | grep postfix
```

If the syslog is empty and you still haven’t received any test email, it’s possible that the test email was rejected by the recipient server. You should check to see if anything has bounced back to your mail folder.

```
sudo less /var/mail/$(whoami)
```

Press uppercase `G` to scroll to the bottom of the file and lowercase `q` to quit. The `$(whoami)` variable returns the currently logged in user.

## Note: Sending Mail to Your Own Domain

If you ever intend to send email from postfix to your own domain, [\[email protected\]](https://devanswers.co/cdn-cgi/l/email-protection) for example, postfix may need some further configuration. Please see article [Can’t send mail to own domain. Postfix: status=bounced (unknown user: “user”)](https://devanswers.co/postfix-statusbounced-unknown-user-user/)