How to Setup Sendmail on Kali Linux & CentOS

This guide will walk you through setting up Sendmail on both Kali Linux and CentOS operating systems. Sendmail is a common Mail Transfer Agent (MTA) used for delivering email on Unix-like systems.

We will cover the necessary steps for installation, configuration, and basic testing of Sendmail on each distribution.

Kali Linux

Installation

Install Sendmail using the following command:

sudo apt-get update
sudo apt-get install sendmail sendmail-cf

Configuration

After installation, configure Sendmail by editing the /etc/mail/sendmail.mc file. Modify the DAEMON_OPTIONS line to listen on all interfaces:

DAEMON_OPTIONS(`Port=smtp, Name=MTA')dnl
dnl to
DAEMON_OPTIONS(`Port=smtp, Name=MTA, Family=inet, Address=0.0.0.0')dnl

Run the following command to regenerate the sendmail.cf file:

sudo m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf

Restart Sendmail

Restart the Sendmail service:

sudo systemctl restart sendmail

CentOS

Installation

Install Sendmail using the yum package manager:

sudo yum update
sudo yum install sendmail sendmail-cf m4

Configuration

Similar to Kali Linux, configure Sendmail by modifying /etc/mail/sendmail.mc. Adjust the DAEMON_OPTIONS:

DAEMON_OPTIONS(`Port=smtp, Name=MTA')dnl
dnl to
DAEMON_OPTIONS(`Port=smtp, Name=MTA, Family=inet, Address=0.0.0.0')dnl

Generate the sendmail.cf file:

sudo m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf

Restart Sendmail

Start and enable the Sendmail service:

sudo systemctl start sendmail
sudo systemctl enable sendmail

Testing Sendmail

You can test Sendmail using the mail command. Replace your_email@example.com with a valid email address:

mail your_email@example.com
Subject: Test Email
This is a test email from Sendmail.
.

The single dot (.) on a line by itself indicates the end of the message.

Check your email inbox to confirm that the email was successfully sent.