Email for Linux Hosts

Updated on 21 Jun 2025.

I wanted my containers / VMs to be able to send emails out to me so that when I installed more complex applications or solutions on top of these platforms, they would be able to provide important feedback.

After doing some tinkering around with OpenSMTPD and not getting it work as I wanted to, I got Postfix working. So this section provides a summary of how I achieved this.

Postfix relay to Gmail

Reference URL:

• Configure Postfix on Linux To Use Gmail SMTP Relay (2023)

• Postfix Documentation

Install and Configure Postfix

$ sudo apt install mailutils libsasl2-modules to install Postfix Edit the /etc/postfix/main.cf configuration file and set the following:

• myhostname = mail.thomas-pk.com

• mynetworks = 127.0.0.1 or 192.168.1.0/24 depending on whether this server will only send out going mail or it works as an smtp relay.

Configure you GMail App Password

Create the /etc/postfix/sasl/sasl_password file, as follows:

• [smtp.gmail.com]:587 yourid@gmail.com:app_password

Then, create a hash map of the password file. This generates the sasl_password.db file.

Then, update the permission so that only root can view or change it with

• $ sudo chmod 0600 /etc/postfix/sasl/sasl_password*

Configure Postfix to use GMail

Edit the /etc/postfix/main.cf configuration file and set the following:

• relayhost=[smtp.gmail.com]:587

• smtp_sasl_auth_enable=yes

• smtp_sasl_security_options=noanonymous

• smtp_sasl_password_maps = hash:/etc/postfix/sasl/sasl_password

Getting ready for the test

In a seperate window, start monitoring the smtp logs with $ sudo journalctl -f _COMM=smtp