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:
Proceed to install Postfix.
To install in Ubuntu, perform:
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 example.com
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:
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:
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 firstname.lastname@example.org
You can search the logs for the information you need via grep, for example, find all the lines that contain email@example.com:
grep firstname.lastname@example.org /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/main.cf
smtp_bind_address = 22.214.171.124
You can also specify on which interfaces Postfix will work:
#inet_interfaces = all
inet_interfaces = 127.0.0.1
Restart Postfix to apply the changes:
sudo /etc/init.d/postfix restart