SMTP is an abbreviation for Simple Mail Transfer Protocol, the standard protocol for transferring emails between servers.
Whenever you type an email and click the send button, you’re transferring data from your computer to the intended recipient’s mailbox. SMTP is the protocol that ensures the data transfer from your computer to the intended recipient’s mailbox. This set of rules instructs different computers how to interact and guides the data to its destination.
Any network-enabled program, including the SMTP server, needs to distinguish between its own data and other packets intended to be processed by different applications. To make the distinction, the system uses ports. Ports are decimal numbers that identify the data chunks for a particular application.
To properly set up your email client or other SMTP software, you need to know the SMTP server name and port number. There are four main ports (25, 26, 465, and 587) that may be used by SMTP applications, and this article will explain how to find out which port number to use.
1. Check Your Email Service Provider’s Documentation
Businesses use email service providers (ESPs) to send bulk emails. Any good ESP must have extensive technical documentation that users can consult to solve their challenges. The documentation clearly states which port number to use.
You can search for terms like “SMTP ports,” “SMTP port numbers,” “email ports,” etc, to find the necessary information.
2. Start With the Default Port Number
You can start with the default port number (587) to see if it’ll work. If not, try port 25. These are the two numbers that almost any SMTP server will support. If they work for you, it means either one is the correct number you’re meant to choose. If not, follow the other steps in this article to find the correct one.
3. Use Telnet to Find It
Telnet is a command line tool that allows users to connect to remote services using specific ports. You can communicate with your email server via the Telnet protocol to find the correct port number.
However, the problem is that Telnet is not enabled by default on Windows 10. To use it, open the Control Panel, then go to Programs and Features and click Turn Windows features on and off in the right panel. Scroll down the list of components to locate Telnet Client, click the checkbox next to it and press Enter.
Now you can proceed with our primary task.
- Launch the command prompt on your PC.
- Type “telnet mail.example.com port-number” on the command line, replacing “mail.example.com” with your SMTP server address and “port-number” with the default port number (587).
- Press the Enter key.
- If 587 is the correct number, Telnet will give you a “220 OK” code indicating a successful connection. If not, repeat the second step, replacing 587 with other port numbers until you get the 220 response.
Consult Your Email Client’s Settings
If you’ve previously set up another email client, you can check its settings to find the right number. The port number will always be visible somewhere in the dialog window.
