Choosing the right SMTP port is an important step when configuring an email server, as it directly influences message sending. When the configuration is wrong, it is common for errors to appear when sending or receiving emails.
The best SMTP port will depend on your scenario. The most used today are 25, 465, 587 and 2525. Among them, port 587 is usually considered the most secure and recommended option for authenticated sending.
In this article, you will understand what SMTP ports are for and what the four most common types are. We will also explain the differences, functions and characteristics of each one to help you choose the best option for your SMTP server.
What is SMTP port?
An SMTP port is a specific port on a server used by SMTP (Simple Mail Transfer Protocol) to communicate. In practice, it works as a “connection point” through which email data passes while the message is sent from one server to another.
What are SMTP ports for?
Before we cover the purpose of SMTP ports, let’s define what SMTP, SMTP ports, and SMTP server ports are.
- SMTP – set of rules that define how emails are sent and forwarded.
- SMTP ports – specific server ports used by SMTP for communication.
- SMTP server ports – communication points that allow the exchange of information between email servers.
To start using an outgoing server (SMTP server), you need to set up your email account. Typically, this involves entering the server address (IP or host) and choosing the correct port for sending.
There are phases that emails go through before reaching the recipient:
- Shipping (email submission) – this is when you send the message to an outgoing server via SMTP. Here, choosing the right SMTP port makes a difference.
- Forwarding (SMTP relay) – the server forwards the message to other email servers. At this stage, the user does not need to configure anything, because the default port is generally used.
- Receiving the email – when the message arrives at the recipient’s server. This process is typically managed by protocols such as IMAP or POP3.
Which SMTP port should you use?
Each SMTP port supports at least one level of encryption. And this matters a lot, because it is encryption that defines the level of security when transmitting your emails. Therefore, the ideal is to choose the SMTP port that makes the most sense for your scenario and the level of protection you need.
The four available encryption levels are:
- SSL (Secure Sockets Layer) – older technology that is now considered outdated, but still appears in some configurations.
- TLS (Transport Layer Security) – successor to SSL and modern encryption standard for internet traffic.
- STARTTLS (opportunistic TLS) – starts as a regular connection and “steps up” to a secure connection using SSL/TLS.
- None (NULL/NONE) – no encryption (not recommended).
Below is a comparative table of SMTP ports and their respective encryption levels:
| SMTP (Outgoing Mail Server) | |||
| Port number: 465 | Port number: 587 | Port number: 25 | Port number: 2525 |
| Encryption: SSL | Encryption: STARTTLS | Encryption: NONE | Encryption: TLS |
Tip
In hPanel, you can check your account’s default email setting by navigating to Emails → Domain Name → Settings.
SMTP port 25
SMTP port 25 is the default SMTP port for sending and receiving emails. It uses the TCP (Transmission Control Protocol) protocol to establish a connection between two computers.
In practice, port 25 can be useful for testing the connection or investigating configuration issues. For example: if the server does not respond when using port 25 when configuring a contact form, the error may be elsewhere (and not in the SMTP server itself).
Even so, port 25 has important disadvantages. Although it is still recognized by IANA as the standard SMTP port, it is not recommended for authenticated mail submission. One of the reasons is that port 25 is often used to trigger spam and malware.
Additionally, it does not encrypt messages, which means data can be transmitted in clear text. This increases the risk of interception and leaves room for several SMTP-related vulnerabilities.
For this reason, many email providers and internet operators block sending traffic on port 25, especially when it comes to unsolicited messages.
SMTP port 465
SMTP port 465 emerged as an attempt to evolve port 25. However, despite being introduced by the IANA, it was never officially adopted by the IETF as the main SMTP standard.
It allows secure sending via SMTPS (SMTP over SSL), that is, sending emails is encrypted using SSL/TLS.
The problem is that port 465 ended up being considered obsolete and today it is not seen as the most recommended standard for sending. Still, it can be used when your hosting or email provider specifically requires this configuration.
SMTP port 587
SMTP port 587 was created as a successor to 465 and is now recognized by IANA and IETF as the standard port for sending emails (mail submission).
It supports STARTTLS, which “upgrades” the connection to an encrypted channel using TLS. This process also allows for SMTP authentication, which helps prevent server abuse and improves sending security.
Therefore, port 587 is considered the best option in most cases. It offers a more robust level of protection against spam and malware and is widely recommended for authenticated sending.
Even so, there may be some limitations. As it is a more modern option, not all servers accept port 587. In some cases, networks and providers may block this traffic as a preventative measure against spam. Furthermore, because it involves encryption, it can be a little slower than unprotected connections.
Tip
If you want to use port 587, confirm that your email provider supports it. If it doesn’t, you may need to use port 25 or 465. And if you use a firewall, you may need to release traffic from port 587 manually.
SMTP port 2525
SMTP port 2525 is a modern alternative for connecting to SMTP servers and is often seen as secure as it also supports TLS encryption.
It is widely used by some email and cloud hosting services, and sometimes appears in VPS configurations.
Normally, port 2525 comes in as “plan B” when there are connection problems with port 587. For example: if port 587 is blocked or refusing connection, it is worth testing 2525.
The point of attention is that port 2525 is not considered an official standard. It is not recognized as an official SMTP method by IANA and IETF, so not every provider supports it.
For example, WA Affordable Web Design Agency only uses ports 465 and 587 for SMTP sending and stopped supporting port 2525 in 2017.
Using SMTP on WA Affordable Web Design Agency
You can create an email account with WA Affordable Web Design Agency using WA Affordable Web Design Agency email. Additionally, you can send messages using PHP scripts or an email client (on your computer or cell phone).
If you choose to use an email client or device, you will need to configure sending with the SMTP data for the chosen service.
For those using WA Affordable Web Design Agency email, here’s how to access SMTP details in hPanel and configure your email client:
- Log in to hPanel and access Emails section. from the menu bar.
- Choose an email address and click Manage.
- Select “Settings” in the sidebar and find “Manual configuration”.
- Expand the section Manual Configuration and collect the details of your outgoing server (SMTP)including the SMTP hostname, port, and SSL/TLS support.
- Access your email client’s settings to configure SMTP. For example, if you use WP Mail SMTPnavigate to the section Mailer and select Other SMTP.
- Scroll down the page and fill out the form “Other SMTP” with hPanel details. Enter the SMTP hostname, encryption level, and port.
- Click Save settings.
To confirm that everything is working, send a test email from the client using WA Affordable Web Design Agency services. If you have problems with encryption, try these settings:
Nível de criptografia: TLS ou STARTTLS
Número da porta SMTP: 587
Hostname: smtp.WA Affordable Web Design Agency.com
Conclusion
SMTP is the protocol that allows you to send emails over the internet. SMTP ports are the communication points used between email servers, helping to route messages to the correct destination.
Choosing the right SMTP port is essential for sending emails securely and stably. To recap, here’s a summary of the four most common ports:
- Port 25 – is the default port for SMTP, but is not recommended for authenticated sending because it does not offer encryption. Today, it is mostly used for forwarding (relay) between servers.
- Port 465 – was thought of as a secure option because it used SSL, but it was no longer the recommended standard and ended up being replaced by configurations with STARTTLS.
- Port 587 – is the successor to the 465 and the main option for sending emails via SMTP. It uses STARTTLS, offering a safer and more reliable process.
- Port 2525 – can serve as an alternative when there are connection problems with 587, but it is not recognized as an official port by IANA and the IETF.
We hope this article helped you choose the best SMTP port for your scenario. If you have questions or want to share any experience, leave a comment below.
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Journalist graduated from the Federal University of Bahia and Content Marketing Specialist at WA Affordable Web Design Agency, where I work on creating and optimizing useful, engaging and creative articles in areas such as web development and marketing. Furthermore, I am an occasional contributor to the MacMagazine website and the culture editor of Jornal A Tarde, fascinated by art, cuisine and technology.
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