Sendmail is a MTA (Mail Transfer Agent) server used for transferring e-mail from between completely different hosts. Sendmail makes use of SMTP protocol. Many of the system administrators most well-liked to make use of Sendmail server as MTA than other MTAs. This tutorial lets you Install Sendmail on Debian 9 (Stretch) Linux system.
1. Install Sendmail
If you don’t have installed Sendmail utilizing the next command to install Sendmail with other required packages utilizing the apt package manager.
sudo apt update sudo apt install sendmail sendmail-cf m4
2. Configure Sendmail Server
Now, execute the sendmailconfig command to finish the basic configuration.
sudo sendmailconfig
Choose all choices to ‘Y’ and press enter. Wait for the command end.
Your server is prepared for sending emails. You should use the Linux command line or PHP script to send emails.
3. Receive Incomming Emails
Edit /etc/mail/sendmail.mc file and comment below line to allow receiving an e-mail from anywhere. To comment a line in sendmail.mc, simply put dnl keyword at the beginning 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')dnlThen add your domains to /etc/mail/local-host-names file.
cat /etc/mail/local-host-names sisrv.net mail.sisrv.net localhost localhost.localdomain
Now use m4 is a macro processor to compile the Sendmail configuration files. m4 is stream-based, that’s, 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 prepared for incoming emails.
Using sendmail from the command line
The following are two examples on how to send email from the command line using sendmail.
Simple example
Once logged in to your web server via SSH, you can run the following command to send email:
[server]$ /usr/sbin/sendmail youremail@example.com Subject: Test Send Mail Hello World control d (this key combination of control key and d will finish the email.)
The above example sends an email as follows:
- The first line indicates the email address sendmail will send the email TO.
- The Subject is 'Test Send Mail'.
- The body of the message says 'Hello World'.
- When the message is received, the FROM email address will appear as your user@server. For example, username@sisrv.net
Adding To and From addresses
This example is the same as the one above, but adds a specific To and From address:
[server]$ /usr/sbin/sendmail youremail@example.com To: differentemail@example.com From: anyone@example.com Subject: Test Send Mail Testing sendmail control d (this key combination will finish the email.)
The above example sends an email as follows:
- The first line indicates the email address sendmail will send the email TO.
- The email you enter into the To field does not receive an email. It only shows as the To address when the actual recipient receives the email. The recipient is still the first email you enter on the first line when running the command, and can also be the same if you wish.
- The From address is what you entered: anyone@example.com.
- The Subject is what you entered: Test Send Mail.
- The body of the message is what you entered: Testing sendmail.
Sendmail in a cgi script
You can also use sendmail in a script as well. This can be done in several languages. The following example shows a perl cgi script.
Create a file name perltest.pl with the following code and make sure the permissions on the file are set to 755 or it will not run:
Note how the To, From, and Subject fields do not end unless the line is ended with \n.
#!/usr/bin/perl use strict; my($mailprog) = '/usr/sbin/sendmail'; my($from_address) ='AnyoneYouWant@example.com'; my($to_address) ='email@example.com'; open (MAIL, "|$mailprog -t $to_address") || die "Can't open $mailprog!\n"; print MAIL "To: $to_address\n"; print MAIL "From: $from_address\n"; print MAIL "Subject: Hello, self. Nice to email myself."; print MAIL "This is still subject line.\n"; print MAIL "This is the body of my message.\n"; print MAIL "Pretty boring, yes?\n"; print MAIL "Goodbye.\n"; close (MAIL);
This example sends an email to email@example.com.
4. Configure Domain-based E-mail Routing
As we learn above that virtusertable file used for aliasing, permitting multiple virtual domains to be hosted on one machine.
- 1. All emails addressed to @example.com domain delivered to help@mydomain.com
@example.com help@mydomain.com
- 2. All emails addressed to help@mydomain.com will ahead to local user jack.
help@mydomain.com jack
- 3. All emails addressed to @mydomain.com will ahead to domain @otherdomain.com with corresponding usernames.
@mydomain.com %1@otherdomain.com
- 4. All emails addressed to @otherdomain.com shall be rejected my mail server with acknowledging sender with the message
@otherdomain.com error:nouser User unknown
After making all modifications in virtusertable execute the next command to create an updated virtusertable.db file containing the new configuration.
sudo makemap hash /etc/mail/virtusertable < /etc/mail/virtusertable
Additionally ensure that the following entry is added in sendmail.mc file.
FEATURE(`virtusertable')
Add entry if not available and compile configuration file
sudo m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf
Now restart Sendmail service
sudo systemctl restart sendmail
Thanks for reading this article. I hope this article will show you how to to Install & configure Sendmail on Debian 9 (Stretch) system.
