What are SMTP Ports?—A Short Guide

by sunel

What are SMTP Ports?—A Short Guide & best SMTP relay service provider

It costs a lot of money and time to successfully use email marketing. Having an email service that enables you to contact your target audience is, without a doubt, something you need.

So, before choosing an email service, it is best to understand SMTP ports, which, in today’s guide, you’ll understand in detail.

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What Does “SMTP Port” Mean?

The Standard Mail Transfer Protocol (SMTP) port is a communication endpoint that manages the transfer of email data from one server to another as it travels over a network. In short, it is a method for allowing computer communication, such as between two mail servers.

In order to get the correct data to the right locations, ports are necessary. Any networked service needs a domain name or internet address and a port in order to properly route messages, whether you’re sending an email or browsing the web.

SMTP Port Types

There are four types of SMTP ports, which are either used for SMTP relay or submission-

Port 25

Port 25 is the first and oldest SMTP port and is also known as the standard SMTP port. However, it is not used in modern SMTP client services such as Gmail, Yahoo, etc. The reason is that many ISPs and cloud providers intentionally block traffic entering on port 25 since it’s an easy route for malicious hackers and malware bots to send spam emails and it’s unsafe.

Port 465

Port 465 enables secure email transfer with SSL, utilising Simple Mail Transfer Protocol (SMTP). Mail transmission on port 465 is protected by implicit TLS, which encrypts the initial connection using a TLS or SSL certificate. The IETF, however, has never formally acknowledged it as an official SMTP port. So, SMTP port 465 is no longer recommended and is not accepted as a standard for mail submission.

Port 587

Modern secure SMTP port 587 was created for message transmission. It supports both STARTTLS and TLS natively, enabling the safe transmission of emails over SMTP.

Today, the majority of contemporary email services, including email service providers and hosting providers, use SMTP port 587 by default. Popular email applications, including Apple Mail and Microsoft Outlook, use Port 587 as well. It is the most widely used and compatible port, making it the ideal solution in many situations.

Port 2525

It is a modern protocol that is used to connect to SMTP servers, and since it offers TLS encryption for email transmission, it is considered a secure option.

Port 2525 is not officially recognised by the IETF or IANA. Still, port 2525 is often used as an alternate to port 587 for SMTP submission, and the majority of cloud hosting providers and ISPs support it. Moreover, it is an acceptable alternative if port 587 is blocked.


Simple Mail Transfer Protocol (SMTP) submission depends on SMTP ports. For this reason, while configuring an email server, it’s critical to select the proper port. A bad setting could result in errors when sending and receiving emails.

It’s possible that a lot of the emails sent by your current provider are marked as spam because of a wrong SMTP port selection. Therefore, taking help from the best SMTP relay service provider can help you prevent this.

At last, SMTP is a little bit of a hard subject to understand for newbies. However, our short, detailed guides about SMTP will give you enough insights with which you can easily understand SMTP.

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