Learn how to set up Linux Sendmail Port 587. Our Sendmail Support team is here to help you with your questions and concerns.

How to set up Linux Sendmail Port 587

In Linux, Sendmail is often used to send outgoing email messages.

Furthermore, port 587 is used for email submission, not for the actual transmission of email between mail servers.

When we configure Sendmail to use port 587, it means that Sendmail will accept incoming email submissions from email clients, and make sure they are authenticated and authorized before allowing the messages to be sent.

This helps prevent unauthorized relay and strengthen email security.

Let’s take a quick look at how to set up Sendmail to listen on port 587 and offer email submission services:

• To begin with, we have to modify the Sendmail configuration to listen on port 587. We have to specify that Sendmail should accept email submissions on this port.
• Furthermore, our experts suggest enabling TLS for port 587 to encrypt the communication between the email client and the Sendmail server. This is important when sending email credentials and messages.
• Then, set up authentication mechanisms for email clients to log in when submitting email through port 587.
• At this point, we have to make sure the firewall on our Linux server allows incoming connections on port 587.

How to set up Sendmail to listen on Port 587

1. First, take a backup of the current functional sendmail.cf and sendmail.mc files.
2. Next, add these lines to sendmail.mc.

   
define(`RELAY_MAILER_ARGS', `TCP $h 587')
define(`ESMTP_MAILER_ARGS', `TCP $h 587')
DAEMON_OPTIONS(`Name=MSA, Port=587, M=E, Addr=0.0.0.0')


   These lines configure Sendmail to listen on port 587 for outgoing email submissions. The DAEMON_OPTIONS line specifies the port and IP address (0.0.0.0 allows all IP addresses). We can change it as needed.
3. Then, rebuild the Sendmail configuration files by running these commands:

   sudo m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf
sudo service sendmail restart
4. Now, we can check if Sendmail is listening on port 587, with the netstat or ss command.

   For example:
   netstat -tuln | grep 587
5. Furthermore, we have to make sure that the firewall allows incoming connections on port 587 if we have a firewall enabled.

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Conclusion

In brief, our Support Experts demonstrated how to set up Sendmail to listen on port 587.