How to setup Simple Mail Transfer Protocol (SMTP) in RHEL 7
How to setup Simple Mail Transfer Protocol (SMTP)
In general, the sender will create the email message and sends to server. Then it will be forwarded to recipient mail server and delivers the mail to client progtram or web mail. The SMTP server service is present in all the servers. In this article we will discuss how to setup Simple Mail Transfer Protocol (SMTP) in RHEL 7.
Test environment
Original mail server and central mail server
Original Mail Server: (hostname: mail.linuxhelp.com / IP: 192.168.5.159)
/etc/hosts file is used for the name resolution.
192.168.5.159 mail.linuxhelp.com mail
::1 mail.linuxhelp.com mail
To install Postfix and Firewall
To Install Postfix
[root@linuxhelp ~]# yum install postfix
Loaded plugins: fastestmirror, langpacks
base | 3.6 kB 00:00:00
extras 3.4 kB 00:00:00
updates 3.4 kB 00:00:00
updates/7/x86_64/primary_db 3.2 MB 00:00:04
Loading mirror speeds from cached hostfile
* base: centos-hn.viettelidc.com.vn
Most of linux distribution postfix is default package
To Start the service
You can enable it to run on the future reboots
[root@linuxhelp ~]# systemctl start postfix
[root@linuxhelp ~]# systemctl enable postfix
To allow mail traffic through the firewall
[root@linuxhelp ~]# firewall-cmd --permanent &ndash add-service=smtp success [root@linuxhelp ~]# firewall-cmd &ndash add-service=smtp success
To Configure Postfix
You can configure postfix on mail.linuxhelp.com. The /etc/postfix/main.cf consists of the postfix main configuration file.
To Configure Postfix on mail.linuxhelp.com.
[root@linuxhelp ~]# vim /etc/postfix/main.cf
myhostname = mail.linuxhelp.com
mydomain = linuxhelp.com
myorigin = $mydomain
inet_interfaces = all
mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
mynetworks = 192.168.5.0/24, 127.0.0.0/8
To Restart the service
[root@linuxhelp ~]# systemctl restart postfix
the servers can be restarted
To troubleshoot
[root@linuxhelp ~]#systemctl status postfix postfix.service - Postfix Mail Transport Agent Loaded: loaded (/usr/lib/systemd/system/postfix.service enabled) Active: active (running) since Thu 2016-03-17 23:56:36 EDT 1min 40s ago Process: 6424 ExecStop=/usr/sbin/postfix stop (code=exited, status=0/SUCCESS) Process: 6439 ExecStart=/usr/sbin/postfix start (code=exited, status=0/SUCCESS) [root@linuxhelp ~]# journalctl -xn -- Logs begin at Thu 2016-03-17 22:21:47 EDT, end at Fri 2016-03-18 00:01:08 EDT Mar 18 00:01:01 linuxhelp systemd[1]: Starting Session 13 of user root. -- Subject: Unit session-13.scope has begun with start-up ... ... ... -- The start-up result is done. Mar 18 00:01:01 linuxhelp CROND[6643]: (root) CMD (run-parts /etc/cron.hourly) Mar 18 00:01:01 linuxhelp run-parts(/etc/cron.hourly)[6649]: start [root@linuxhelp ~]# postconf -n alias_database = hash:/etc/aliases alias_maps = hash:/etc/aliases command_directory = /usr/sbin config_directory = /etc/postfix daemon_directory = /usr/libexec/postfix data_directory = /var/lib/postfix debug_peer_level = 2 debugger_command = PATH=/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin ddd $daemon_directory/$process_name $process_id & sleep 5 html_directory = no inet_interfaces = localhost inet_protocols = all mail_owner = postfix ..... .....
To test Postfix Mail Servers
Mail User Agent can be used to test the mail servers.
[root@linuxhelp ~]# mail -S " hai" user1@linuxhelp.com
Subject: invite
wellcome to linuxhelp tutoraial...
.
EOT
To check if email is received
Go to central mail server and log on as user
[root@linuxhelp ~]# su - user1
[user1@linuxhelp ~]$ mail
Heirloom Mail version 12.5 7/5/10. Type ? for help.
" /var/spool/mail/user1" : 2 messages 1 new 2 unread
U 1 root Thu Mar 17 22:51 21/590 " hai"
> N 2 root Fri Mar 18 00:14 18/606 " invite"
& ^Cinterrupt
You have mail in /var/spool/mail/user1
To check the mail content
[user1@linuxhelp ~]$ vim /var/mail/user1
From root@linuxhelp.com Fri Mar 18 00:14:21 2016
Return-Path: < root@linuxhelp.com>
X-Original-To: user1@linuxhelp.com
Delivered-To: user1@linuxhelp.com
...
...
Message-Id: < 20160318041421.397E46316722@mail.linuxhelp.com>
From: root@linuxhelp.com (root)
Status: O
welcome to linuxhelp tutorial...
If mail is not received, check root mail spool for error notification.
to troubleshoot the Postfix.
End-to- end method
Store-and- forward method
The end to end model is used to communicate between different organizations whereas the store and forward method is used within an organization