How to Install Sendmail on Fedora 29/28/27

Sendmail is a general purpose email routing facility used for email transport over the Internet. It includes SMTP (Simple Mail Transfer Protocol) for the mail-transfer and email delivery. Most of the system administrators preferred to use Sendmail server as MTA than other MTAs. You can also use Sendmail server to send the email via external SMTP servers like Gmail, Amazon SES, MailChimp etc.

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.

sudo dnf install sendmail sendmail-cf

2. Configure Sendmail on Fedora

Before starting configuration we must know about various Sendmail configuration files exists in /etc/mail directory.

• access — Allow/Deny other systems to use Sendmail for outbound emails.
• domaintable — Used for domain name mapping for Sendmail.
• local-host-names — Used to define aliases for the host.
• mailertable — Defined the instructions that override routing for particular domains.
• virtusertable — Specifies a domain-specific form of aliasing, allowing multiple virtual domains to be hosted on one machine.

2.1 Comment out below line in /etc/mail/sendmail.mc to allow receiving email from anywhere. To comment a line in sendmail.mc, just put dnl at start of line.

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

FEATURE(`relay_hosts_only')dnl

2.3 Add your PC’s full hostname in this file.

hostname >> /etc/mail/relay-domains

3. Recompile Configuration File

m4 ia a macro processor to compile the Sendmail configuration files. m4 is stream-based, that is, it doesn’t understand about lines.

sudo m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf

Restart Sendmail service

sudo systemctl restart sendmail

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 [email protected]

  @example.com [email protected]
  

• 2. All emails addressed to [email protected] will forward to local user jack.

  [email protected]  jack
  

• 3. All emails addressed to @mydomain.com will forward to domain @otherdomain.com with corresponding usernames.

  @mydomain.com    %[email protected]
  

• 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

Finally, restart the Sendmail service to apply changes

sudo systemctl restart sendmail

Thanks for reading this article. I hope this article will help you to configure Sendmail on CentOS and Red Hat systems.

References:
http://www.sendmail.com/
http://www.sendmail.com/sm/open_source/docs/m4/intro_m4.html