Sendmail is a MTA (Mail Transfer Agent) server used for transferring email from between different hosts. Sendmail uses SMTP (Simple Mail Transfer Protocol) protocol. Most of the system administrators preferred to use Sendmail server as MTA than other MTAs.
RHEL 5 or its earlier versions were using Sendmail as a default mail server, But newer version’s of RHEL based systems adapted postfix as a default mail server. Most of the users are familiar with Sendmail and want to use it with version 6 also. This article will help users for installing Sendmail server on RHEL 7/6/5 or with minimal configuration.
1. Install Sendmail
If you don’t have installed Sendmail using the following command to install Sendmail with other required packages using yum package manager.
yum install sendmail sendmail-cf m4
2. Configure Sendmail Server
Before starting configuration we must know about various Sendmail configuration files exists in /etc/mail directory.
2.1 Comment out below line in
dnl DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl
2.2 Add this line also in sendmail.mc above ‘MAILER’ option
2.3 Add your PC’s full hostname in this file.
hostname >> /etc/mail/relay-domains
3. Recompile Sendmail Configuration
m4 ia a macro processor to compile the Sendmail configuration files. m4 is stream-based, that is, it doesn’t understand about lines.
m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf
Restart Sendmail service
4. Configure Domain-based E-mail Routing
As we read above that virtusertable file used for aliasing, allowing multiple virtual domains to be hosted on one machine.
1. All emails addressed to @example.com domain delivered to firstname.lastname@example.org
2. All emails addressed to email@example.com will forward to local user jack.
3. All emails addressed to @mydomain.com will forward to domain @otherdomain.com with corresponding usernames.
4. All emails addressed to @otherdomain.com will be rejected my mail server with acknowledging sender with the message
@otherdomain.com error:nouser User unknown
After making all changes in virtusertable execute following command to create updated virtusertable.db file containing the new configuration.
makemap hash /etc/mail/virtusertable < /etc/mail/virtusertable
Now restart Sendmail service
Thanks for reading this article. I hope this article will help you to configure Sendmail on CentOS and Red Hat systems.