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. Remove Postfix
Postfix is the default SMTP service pre-installed on Ubuntu operating systems. And you are willing to use Sendmail server on your system.
First of all, remove the existing postfix installation on Ubuntu.
sudo systemctl stop postfix sudo apt remove postfix && apt purge postfix
2. 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 apt install sendmail
3. Configure Sendmail Server
The execute the sendmailconfig command to complete the basic configuration.
Select all options to ‘Y’ and press enter. Wait for the command finish.
4. Receive Incomming Emails
Edit /etc/mail/sendmail.mc file and comment below line to allow receiving an email from anywhere. To comment a line in sendmail.mc, just put dnl keyword at the start of the line.
dnl DAEMON_OPTIONS(`Family=inet, Name=MTA-v4, Port=smtp, Addr=127.0.0.1')dnl dnl DAEMON_OPTIONS(`Family=inet, Name=MSP-v4, Port=submission, M=Ea, Addr=127.0.0.1')dnl
Then add your domain names to /etc/mail/local-host-names file.
cat /etc/mail/local-host-names tecadmin.net mail.tecadmin.net localhost localhost.localdomain
Now use m4 is 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
Your system is ready for incoming emails.
5. 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.
sudo makemap hash /etc/mail/virtusertable < /etc/mail/virtusertable
Now restart Sendmail service
sudo /etc/init.d/sendmail restart
Thanks for reading this article. I hope this article will help you to configure Sendmail on CentOS and Red Hat systems.