Installing and Configuring Postfix

Postfix — mail transfer agent (MTA) with open source.

Assume that the IP address of the server is configured with a domain name, from which the mail will be sent in the future.

Switch directly to the root user:

sudo -i

Proceed to install Postfix.
To install in Ubuntu, perform:

apt-get update
apt-get install postfix

For installation in CentOS:

yum install postfix

During the installation, some questions will be asked.
1) Choose the “Internet site”
2) Specify the fully qualified domain name server (FQDN), for example

After that Postfix will start working.
Configuration files are usually found in /etc/postfix.

We can look at the status/restart/stop/start Postfix commands:

service postfix status
service postfix restart
service postfix stop
service postfix start

If necessary, you can reconfigure by typing the following command:

dpkg-reconfigure postfix

Let’s see if the ports are used:

netstat -na | grep LISTEN | grep 25
netstat -na | grep LISTEN | grep 587

You can perform an automatic check:

postfix check

Let’s try to send the letter to the specified address (after the command we will type the desired text and put a point for completion):

sendmail -v

You can search the logs for the information you need via grep, for example, find all the lines that contain

grep /var/log/mail.log

You can also connect from another host to the postfix port via telnet and make sure that it is running.

For diagnostics, you can observe the connections using tcpdump:

tcpdump port 25
tcpdump port 587

If there are more than one IP on the server, and the domain is only on one, we will specify from which IP the sending will be done:

sudo nano /etc/postfix/
smtp_bind_address =

You can also specify on which interfaces Postfix will work:

#inet_interfaces = all
inet_interfaces =

Restart Postfix to apply the changes:

sudo /etc/init.d/postfix restart
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