postfix s a free and open-source mail transfer agent (MTA) that routes and delivers electronic mail.

1). First, we install postfix on server.

yum install postfix

 In case Sendmail is installed, erase it or stop the services of sendamil.

yum remove sendmail

or

 service stop sendmail

chkconfig sendmail off

2). After installation configure Postfix.

“/etc/postfix/main.cf” is main configuration file.

Uncomment below line and do needful entry as per environment

mynetworks

mydomain

myhostname

relayhost

3) We also need to add our server IP into Exchange server for communication.

4).Then restart postfix services.

service postfix start

Enabled postfix service so that automatically start after reboot server.

chkconfig postfix on

5). for testing purpose, make entry postfix server ip in client server and send mail.

Troubleshooting step.

• First, check can we able to telnet on 25 port postfix server to exchange server.
• After configuration or restart postfix services, check 25 port through any client to postfix server.
• Log location /var/log/maillog

Prerequisite for postfix server.

• Should be entry of DNS server.
• Also server entry should be present on DNS server
• Postfix server IP entry should be present on exchange server.
• Port 25 should be open for server to exchange server.

After configure postfix server , any client should able to connect on port 25 if not present then coordinate with Network team (Any firewall present betw