Postfix Installation and Configuration

CentOS & Ubuntu / Debian

#CentOS
yum update -y && yum upgrade -y
yum install postfix -y

#Debian / Ubuntu
apt update && apt upgrade -y
apt install postfix -y​

Make sure the libsasl2-modules package is installed and up to date:

apt-get install libsasl2-modules​ -y

Once the installation is finished, open the /etc/postfix/main.cf file with your favourite text editor:

nano /etc/postfix/main.cf

Check for the hostname. It should be your fqdn.

nano /etc/postfix/main.cf ​

Open or create the /etc/postfix/sasl_passwd file, using your favorite text editor:

nano /etc/postfix/sasl_passwd

Add your destination (SMTP Host), username, and password in the following format:

/etc/postfix/sasl_passwd

[mail.isp.example]:587 username:password​

Create the hash db file for Postfix by running the postmap command:

postmap /etc/postfix/sasl_passwd

If all went well, you should have a new file named sasl_passwd.db in the /etc/postfix/ directory.

Secure the password database

chown root:root /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db
chmod 0600 /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db
​

Open the /etc/postfix/main.cf file with your favorite text editor:

nano /etc/postfix/main.cf

Setup Relayhost

# specify SMTP relay host
relayhost = [mail.isp.example]:587

At the end of the file, add the following parameters to enable authentication:

# enable SASL authentication
smtp_sasl_auth_enable = yes
# disallow methods that allow anonymous authentication.
smtp_sasl_security_options = noanonymous
# where to find sasl_passwd
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
# Enable STARTTLS encryption
smtp_use_tls = yes
# where to find CA certificates
smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt

To change the system user full name.. Please change the name here

/etc/passwd


root:x:0:0:System - Jetztrufen:/root:/bin/bash

To merge FROM Address into your define email ID.

In /etc/postfix/main.cf add this line at the bottom.

smtp_generic_maps = hash:/etc/postfix/generic

And then in /etc/postfix/generic . Add the line for the originating email address, and the email address you want it to appear to be from

chown root:root /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db
chmod 0600 /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db

and then run the following postmap command to re-generate the map:

postmap /etc/postfix/generic​

At the end please remember to restart postfix.

service postfix restart​