Email is the largest online communication medium, with over 4 billion active users globally. This massive exchange of information is powered by the Simple Mail Transfer Protocol (SMTP).
While setting up your email app, it’s essential to choose the right port number. This article will explain how to do that.
What is an SMTP port?
SMTP is the standard protocol for relaying data between mail servers. When you type an email and hit send, you’re technically transferring the message from your mail server to that of the recipient. A port is the communication endpoint facilitating this data transfer.
Why is it important?
Three things happen to your email when you hit the send button.
- Submission: Your email client submits the message to your local SMTP server.
- Relaying: After submission is confirmed, the relay begins, transferring the data to the recipient’s SMTP server.
- Retrieving: The recipient’s email client fetches the email from their server.
The SMTP protocol powers the submission and relaying stages. To transmit data to its destination, the SMTP software needs to know the receiving party’s IP address and port number. The former identifies a particular computer, while the latter defines which kind of application will process the incoming data.
What are the available ports?
There are four main ports used for SMTP data transfer: 25, 465, 587, and 2525. If your email administrator hasn’t provided you with a proper port number, you may try some of these, as described below. Don’t worry – if you enter a wrong port number, you won’t break anything, email submission just won’t work as it should.
25
This port was the earliest one to be adopted. It doesn’t support data encryption. Because this is the default endpoint for relaying and lacks security, many spammers and malicious actors abuse it to send harmful messages. Thus, many internet service providers (ISPs) and email service providers (ESPs) have disabled it for security reasons.
465
This port was introduced as an upgrade to 25. Unlike 25, it supported encrypted connections via the Secure Sockets Layer (SSL) protocol. 465 served its function well but was later deprecated in favor of another port, 587.
587
This is currently SMTP’s default port for email submission, as recognized by the Internet Assigned Numbers Authority (IANA) and Internet Engineering Task Force (IETF). This port supports encrypted connections via the Transport Layer Security (TLS) protocol, the successor to SSL.
2525
This endpoint is rather tricky, as the IANA and IETF do not formally recognize it. Yet, most ISPs and ESPs support it. It’s a suitable alternative when 587 is not available for whatever reason.
The bottom line
Ports 587 and 2525 are the first ones you should try when setting up your email client. 25 is almost never used for submission these days, and 465 has long been deprecated in favor of 587.
You shouldn’t have any problems using 587 or 2525, but you’ll likely face issues if you choose 25 or 465. Keep the above in mind, and you’ll likely have a positive experience with your emails.
