Install and configure nullmailer using Fastmail as a smarthost

If you want to receive status updates from your Debian or Ubuntu system, you need to employ the help of a mail tansfer agent (MTA). nullmailer is a relay-only forwarding MTA that can be used as an alternative to more complex MTAs such as Exim, Sendmail or Postfix.

nullmailer can be configured to use Fastmail as a smarthost and hence ensure the deliverability of your messages. In principle, these instructions should also be applicable to service providers other than Fastmail.

In the following example configuration, debian is the hostname, bookworm the local username and linus.torvalds@fastmail.com the Fastmail username.

Step 1

Log into your Fastmail account and set up a new app password for SMTP authentication.

Step 2

Create the new directory /etc/nullmailer and the file /etc/nullmailer/adminaddr.

$ sudo mkdir /etc/nullmailer && sudo nano /etc/nullmailer/adminaddr

Your Fastmail username is the only entry in /etc/nullmailer/adminaddr.

linus.torvalds@fastmail.com

Step 3

Install the required packages.

$ sudo apt-get install --yes nullmailer mailutils

Step 4

Perform the initial configuration using debconf. Reconfigure nullmailer at any time after the initial installation using the following comand.

$ sudo dpkg-reconfigure nullmailer

Setting the mail name

Set the system mail name. If you are setting up on a home network, you should use home.arpa as the domain name.

Configuring nullmailer

Mailname of your system:

debian.home.arpa

Ok

Configuring the smarthost

Set the Fastmail server as the smarthost. Use the app password you set in Step 1.

Configuring nullmailer

Smarthosts:

smtp.fastmail.com smtp --port=587 --auth-login --starttls --user=linus.torvalds@fastmail.com --pass=password

Ok

Step 5

Test your configuration with the following command.

$ echo "Test mail from nullmailer on debian.home.arpa to the local root user and forwarded on to Fastmail" | mail -s "Test nullmailer" root

Check your Inbox, Linus!

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