Configure Postfix MTA as Send-Only on Debian 11¶

1 Setup server hostname¶

The hostname of the server will be used as the name of the sender of the emails. So you should keep it nice and clean

# get the current hostname
hostname

# if the name does not fit you, you can set up a new hostname
sudo hostnamectl set-hostname smtp.casd.local --static

2Install the packages¶

# Install mailutils package
sudo apt install mailutils

# install postfix
sudo apt install postfix

As the postfix package installs, you’ll be asked to select an option on screen for your mail server. For General type of email configuration window, select Internet site and click OK button. Here we suppose your server has internet connexion.

The next page will ask you to set your Mail server name, this can be domain or server hostname with an A record. In this tutorial, we choose the host name of the server smtp.casd.local.

3. Configure Postfix MTA Server¶

Edit Postfix configuration file /etc/postfix/main.cf to ensure it is configured as send only ( Only relaying emails from the local server).

Set Postfix to listen on the 127.0.0.1loopback interface. The default setting is to listen on all interfaces

# open the conf file
sudo vim /etc/postfix/main.cf

# edit the below line
inet_interfaces=loopback-only
myhostname=smtp.casd.local

# restart the postfix service
sudo systemctl restart postfix

4. Test the postfix service¶

To test email delivery, use the mail command like below.

# send a mail to userx@example.com with title `Postfix Testing` and content `Postfix Send-Only Server`
echo "Postfix Send-Only Server" | mail -s "Postfix Testing" userx@example.com

Check the junk mails, you may find it there.