expn command not found

Introduction

When you run more command in linux terminal / console, you get the following error message

expn: command not found

or when using sudo you get the following error message

sudo: expn: command not found

Solutions to expn: command not found

How To Fix expn: command not found in Ubuntu / Debian / Kali Linux / Raspbian

In Ubuntu expn is provided by sendmail-base package.

sendmail-base is:

Sendmail is an alternative Mail Transport Agent (MTA) for Debian. It is suitable for handling sophisticated mail configurations, although this means that its configuration can also be complex.

This package contains the base, architecture independent, portions of the sendmail packages.

To fix this problem, we can install more using the command below.

sudo apt-get -y install sendmail-base

This command might take some time to finish depending on your machine internet connection.

You can also use apt command to install sendmail-base.

sudo apt -y install sendmail-base

Or if you have aptitude installed you can use the following command.

sudo aptitude install sendmail-base

Summary

In this tutorial we learn how to fix expn command not found error in Ubuntu / Debian / Kali Linux or Raspbian distribution.