SMTP Ports

SMTP (Simple Mail Transfer Protocol) is the standard for handling email transmission. It has been around since the 1970s, and modern email clients continue to use it for processing outgoing communication.

SMTP can work on four networking ports: port 25, port 465, port 587, and port 2525. Let’s see what the difference between them is.

Differences between networking ports 

Port 25

When the protocol was first released, port 25 was assigned to it, and it continues to be recognized as the default option for establishing SMTP connections. However, using it to connect your email client to your mail server is not advisable.

Because port 25 is the default SMTP port, it has historically served as the starting point for many spam campaigns launched by compromised computers and servers. To limit the number of unsolicited messages, many ISPs and hosting providers block connections on port 25. 

As a result, setting up your client to work with it might not be possible at all. Even if it is, the connection you establish through it will not be encrypted, meaning all the data will be transmitted in plaintext and will be vulnerable to eavesdropping.

Port 465

Port 465 was assigned by the Internet Assigned Number Authority (IANA) as the default port for a more secure version of SMTP called SMTPS. SMTPS uses Secure Socket Layer (SSL) to encrypt the communication flowing between the client application and the mail server.

By setting up your mail client to connect to the server via port 465, you can ensure that your email communication will be protected. The port has since been assigned a different function, but it continues to be used by many hosting providers as the default SMTP-over-SSL solution.

Port 587

Port 587’s job is to replace port 465 as the default port for secure SMTP connections. Modern email applications recognize it, and it’s accepted by most email delivery services. In combination with a TLS (Transport Layer Security) connection, port 587 is a secure vehicle for processing email communication.

Port 2525

Port 2525 is not recognized as an official SMTP port. However, it is widely acknowledged as an alternative to ports 465 and 587. Unless it’s blocked by an upstream provider, you should be able to use port 2525 with a TLS connection to manage your emails securely.

Which port should I use?

ScalaHosting customers can find all the information they need to set up a connection to their email account (including the SMTP server and the port) in the Welcome Email they receive upon signing up. A copy of it is available in the My Details > Email History section of their Client Area.

Feel free to contact our technical support specialists if you have any further questions.



Working in the web hosting industry for over 13 years, Rado has inevitably got some insight into the industry. A digital marketer by education, Rado is always putting himself in the client's shoes, trying to see what's best for THEM first. A man of the fine detail, you can often find him spending 10+ minutes wondering over a missing comma or slightly skewed design.

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