SMTP Port: How to Choose Correct Port (25, 587, 465, and 2525)

by | Last Updated Jan 8, 2021 | WordPress | 0 comments

Are you trying to figure out which SMTP port to use?

Let’s say you are sending emails using an email client like Outlook or Thunderbird. In such a case, your email client will likely also upload your outgoing emails using SMTP.

These apps usually use other protocols, such as POP3 or IMAP, to download incoming emails to the clients.

Are you struggling with email deliverability on WordPress? Using an SMTP sender like Sendinblue is one of the most powerful ways to solve your problem.

If you set up SMTP through an email client or WordPress site, you’ll likely encounter the question of which SMTP port to utilize.

We will examine everything SMTP-related in this post to help you choose the right SMTP port.

What Is an SMTP Port?

SMTP stands for Simple Mail Transfer Protocol. SMTP is the standard protocol used to send an email on the web.

Emails are sent and received over the Internet using SMTP.

When you send an email, an email client uploads the email to the outgoing mail server.

The outgoing mail server then has to make your email available to the recipient’s incoming mail server.

Mail servers work similarly to website servers.

There may be a user-friendly front-facing domain name. However, the actual communications happen over IP addresses, like 3.7.1.160.

Ports allow computers to communicate with each other. An example is a communication between two mail servers.

  • IP addresses identify computers.
  • Ports identify applications and services running on a computer, such as SMTP.

Here’s a human-friendly analogy.

IP addresses are the street addresses of an office building. A port is the identification number of a specific business within that business complex.

If you want to get something to that company, you can’t just send it to the business complex. You will also need a way to ensure it gets to the right place within the business complex.

The organization managing global IP address allocation and other tasks is the Internet Assigned Numbers Authority (IANA).

IANA is also accountable for allocating port numbers to standard Internet services, including SMTP.

Why Is Your SMTP Port Important?

If you wish to connect directly, you will need to enter both the IP address and the SMTP Server port number.

However, many standard SMTP ports are available, and not all of them function in all situations.

For example, ISPs and cloud providers often block port 25, the standard SMTP port for transferring communications between mail servers.

At Rovity, we also block Port 25.

Because so many services block port 25, if you attempt to connect to an SMTP server via port 25, you’ll usually encounter problems.

Various Ports for Different Purposes

Additionally, each SMTP port has a different purpose. SMTP transmission consists of two broad stages.

  • Submission: Submission means sending an outgoing email message. Whenever you send an email in Gmail, the message must pass through the outgoing mail server.
  • Relay: The communication between two servers. The outgoing server relays the email to the mail server of the recipient after sending/submitting it.

The “submission” part of the process is the most crucial part of setting up your email client or WordPress site.

However, although “relay” is a critical SMTP component, most people don’t need to configure their email server.

What Is the SMTP Port Number?

There is no single SMTP port on the modern web. SMTP uses four standard ports instead.

  • 25
  • 587
  • 465
  • 2525

Let’s go through them one by one.

Why Do We Use Port 25?

The oldest SMTP port is Port 25, which was established in 1982.

Port 25 is still used mostly for SMTP relay and is commonly known as the standard SMTP port.

However, suppose you’re setting up an email client or your WordPress site via SMTP.

In that case, it is generally not recommended to use port 25 since most domestic ISPs and cloud hosting providers block port 25.

Why?

Because port 25 has often been abused by compromised computers to send spam.

Remember that SMTP submission and relay are two different things.

So while SMTP port 25 is sufficient for relaying SMTP messages, it is not a good option for sending them.

Why Do We Use Port 587?

The modern web uses port 587 for SMTP submission.

While you can use other submission ports, port 587 is generally the best port to start. Port 587 is the default and only uses a different port if it is necessary.

For example, if your host blocks port 587 for some reason, then use other ports.

TLS is also supported on Port 587, meaning you can submit secure mail.

Why Do We Use Port 465?

Port 465 was initially assigned for SMTPS (SMTP over SSL).

After being used for that function for only a short time, port 465 was reassigned for a different purpose and deprecated.

However, many ISPs and cloud hosting providers still support SMTP submission over port 465.

Why Do We Use Port 2525?

Port 2525 is not a recognized SMTP port (by the IANA or IETF).

Yet, it’s still widely used for SMTP submission as an alternative to port 587.

Most SMTP servers and ISPs support port 2525 for SMTP.

If port 587 is blocked, port 2525 would be a good option.

What SMTP Port Should You Use?

We talked about this already, but let’s go over it again because it’s crucial to decide correctly.

Suppose you want to set up your WordPress site or email client to use SMTP (submission) to send emails. In that case, use port 587 almost always.

Again, this would be the default SMTP port for submission, and the transmission would be secure via TLS.

Port 2525 is a common alternative to port 587 if port 587 is blocked for some reason.

Again, this isn’t an officially recognized SMTP port but is commonly supported and used by most providers.

Though many providers support port 465 for SMTP, it’s no longer an accepted standard. So always use port 587 and 2525 instead of port 465.

Finally, you should not use port 25 for email clients or WordPress websites when setting up the SMTP relay protocol. Most ISPs and cloud hosts block port 25.

Which SMTP Ports Does Rovity Support?

At Rovity, you can use the following ports.

  • 587
  • 465

You cannot use port 25 because Rovity blocks unauthorized access to it.

Summary

SMTP is an essential component of email transmission over the Internet.

You can set up your WordPress site to send transactional emails through SMTP to improve deliverability.

Additionally, let’s say you use Gmail or Outlook. In this case, your email client sends outgoing messages via SMTP.

It is necessary to enter a specific SMTP port to connect your WordPress site or email client to the SMTP server.

SMTP has four standard ports.

  • 25
  • 587
  • 465
  • 2525

Port 25 is generally used for SMTP relay, but most providers block it for SMTP submission.

Do you wish to configure your WordPress website or email client to send emails using SMTP?

Then you should first use port 587. Port 587 is a standard SMTP submission port.

You can try port 2525 if port 587 doesn’t work. It isn’t an official SMTP port, but it’s widely supported and has TLS support for secure communications.

We engineered our cloud infrastructure with Performance, Speed, Scalability, and Security in mind.

That’s why we built Rovity with AWS, CloudLinux OS, DirectAdmin, and LiteSpeed Web Server.

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By Jafar Muhammed

Jafar Muhammed has 10+ years of experience in WordPress, web hosting, domain names, DNS, CDN, server administration, etc. He is an open web advocate. He is the CEO of Rovity, the fastest growing premium shared hosting startup in India.

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