What Simple Mail Transfer Protocol (SMTP) port should be used? (short answer)
When setting up SMTP for sending emails, picking the right port is important for both security and getting your emails delivered. The most common ports are 25, 465, and 587, and each one has a different job.
For most cases, port 587 is the best choice. It works with STARTTLS, which makes the connection secure by encrypting the email. This helps protect your emails from being stolen during sending. Port 587 is widely used and is the standard for secure email sending.
Port 25 used to be the main port for sending emails, but it’s now mostly outdated. ISPs often block it to stop spam, so it’s not recommended for sending emails anymore. It’s still used for server-to-server communication, but not for email clients.
Port 465 was once used for secure email (SMTPS), but it’s been replaced by STARTTLS on port 587. Some providers still use it for old systems, but it’s less common now.
If the regular ports are blocked, you can use port 2525 as a backup. It’s not officially recognized but can help when other ports aren’t available.
Illustration depicting the SMTP port
Choosing the right SMTP port helps you follow your email provider’s rules and improve email deliverability. Port 587 is the best choice. It’s secure, reliable, and works well for sending emails today.
Different Ports In Mail Servers for Different Purposes
SMTP (Simple Mail Transfer Protocol) is key to email communication. However, not all SMTP ports are the same. Each port serves a specific role in internet communication. Knowing the differences can help you set up your email for better performance and security.
Port 25 is the oldest SMTP port. It was used for email relay, moving emails between servers. However, it’s now often blocked by ISPs because it’s vulnerable to spam and phishing attacks.
Port 465 was used for SMTPS (SMTP over SSL), which provided a secure connection from the start. The IETF deprecated this port, but some email providers still use it for compatibility with older systems.
Port 587 is now the standard SMTP port for sending emails. It’s used for submitting emails from clients like Apple Mail or Outlook to a mail server. This port uses TLS encryption, which keeps your emails safe during transmission.
Port 2525 is an alternative. It’s used when standard SMTP ports are blocked. Though not officially recognized by the IANA, it works similarly to Port 587 and can be a good backup.
Illustration depicting a person choosing a SMTP port
Each of these ports has its purpose and choosing the right one depends on the specific needs and restrictions of the user’s network and email client. Whether it’s achieving better email deliverability, complying with email servers‘ security standards, or navigating ISP restrictions, selecting the appropriate SMTP port is a critical decision in email transmission.
SMTP Port 25
SMTP Port 25 has played a foundational role in the history of email communication, but its use has evolved significantly over the years due to changes in security practices and standards.
What is Port 25 Used For?
Port 25 was once the default SMTP port for sending emails across the internet. It allowed email servers to relay messages to one another, with minimal security checks. This worked well in the early days of the internet when trust was high and security threats were low.
The main job of Port 25 is to let email servers talk to each other, forwarding emails from one server to another. It doesn’t use encryption, so it’s not secure for sending emails from a client to a server.
Port 25 is Deprecated
Today, Port 25 is mostly outdated for sending emails directly from email clients. It became a target for spammers because it didn’t have encryption, making it easy to intercept and misuse.
Now, most internet service providers and email servers block Port 25 to prevent abuse. Email providers recommend using more secure ports like Port 587 or Port 465, which use TLS encryption. This improves security and helps ensure your emails reach their destination without getting caught in spam filters.
For these reasons, you should avoid using Port 25 for email submissions. It’s now mostly used for internal network email transport or between trusted mail servers.
SMTP Port 465
SMTP Port 465 is often surrounded by some confusion due to its history and the changes in protocol standards over the years.
What is Port 465 Used For?
Port 465 was made for SMTPS (SMTP Secure), which used SSL to secure the connection right from the start. Unlike STARTTLS, which upgrades the connection, SMTPS encrypts the SMTP session from the beginning.
Port 465 creates an encrypted channel between the email client and server, keeping data secure and private. This was crucial as email security became more important.
However, the IETF deprecated Port 465 in favor of STARTTLS on Port 587. STARTTLS allows both regular and encrypted communication over one port, making it more flexible.
Although Port 465 is no longer the standard, many email providers still support it for compatibility. It’s mainly used where instant SSL/TLS encryption is needed.
If your email setup supports SMTPS, Port 465 can still work. Just ensure both the client and server support it and that it doesn’t conflict with newer security protocols.
SMTP Port 587
SMTP Port 587 is pivotal in modern email communication, designed specifically for email submission in a way that ensures secure and reliable delivery.
What is Port 587 Used For?
Port 587 is used for email submission, allowing emails to go directly from clients to servers. It’s the recommended port for mail clients like Microsoft Outlook or Apple Mail. Unlike Port 25, which is for server-to-server email relay, Port 587 submits messages directly to an email server, which then relays them.
This port is important because it supports the STARTTLS command. STARTTLS upgrades a plain connection to a secure one, using TLS encryption. This makes Port 587 the preferred choice to protect outgoing emails from eavesdropping and tampering.
The original default SMTP port for sending emails
Port 587 is the default mail submission port. It’s recognized by the Internet Assigned Numbers Authority (IANA) and endorsed by the Internet Engineering Task Force (IETF) for modern email transmission practices focused on security.
Port 587 was created to offer a reliable method for email submission, avoiding the problems of Port 25, such as its abuse by spammers and frequent blocking by internet service providers.
TCP Port 587: Exploring Technical Details
TCP Port 587 uses the Transmission Control Protocol (TCP) to ensure that all data is received by the server in the correct order and without loss. This is crucial for keeping encrypted messages intact, as even small data loss or changes can affect encryption.
To configure your SMTP server to use Port 587, specify the port in your email client’s or application’s settings. It usually requires authentication, meaning you need to provide credentials before sending emails. This helps prevent unauthorized access to the email service.
Additionally, Port 587 typically requires a secure connection from the start or upgrades to a secure one using STARTTLS before sending any data. This enhances the security of your messages while in transit.
SMTP Port 2525
SMTP Port 2525 is not as widely recognized as the other SMTP ports, but it serves a crucial role for users facing specific network restrictions
What is Port 2525 Used For?
Port 2525 is often used as an alternative to standard SMTP ports, especially when ports like 587, 465, or 25 are blocked by network administrators or internet service providers. Email service providers offer Port 2525 as an extra option to ensure clients can still send emails when traditional ports are unavailable.
Like Port 587, Port 2525 supports SMTP with STARTTLS, which upgrades a plain connection to a secure one. This encryption protects email data before it’s sent, making Port 2525 a versatile and secure option for email submission.
An Alternative SMTP Port
While Port 2525 is not officially recognized by the Internet Assigned Numbers Authority (IANA), it’s widely used as a practical alternative in many modern email systems. It works similarly to Port 587, offering a fallback for users who face port restrictions that hinder email communication.
Port 2525 is especially useful in restricted environments, like corporate networks or countries with heavy internet controls. For businesses or individuals who need reliable email delivery, configuring their systems to use Port 2525 ensures continuous, uninterrupted service.
Why Does Your SMTP Port Matter On Your Mail Server?
Illustration of the importance of a SMTP port
Selecting the correct SMTP port is not merely a technicality—it is a crucial decision that impacts the security, reliability, and effectiveness of your email communication strategies.
Why your choice of SMTP port matters
Choosing the right SMTP port impacts how your emails are sent and received. It ensures compliance with the standards set by email servers and ISPs, reducing the risk of your emails being flagged as spam. The port you select affects both the security of your data and the speed and reliability of email delivery.
SMTP Ports
SMTP Port 25Port 25 is widely considered a deprecated port for sending emails directly from email clients.SMTP Port 465Port 465 was originally designated for SMTPS. While Port 465 is no longer recommended as a standard by the IETF, it continues to be supported by many email service providers for backward compatibilitySMTP Port 587This port is critical because it supports the STARTTLS command, which means it can upgrade an initially plaintext SMTP connection to a secure connection using TLS encryption.SMTP Port 2525SMTP Port 2525 is not as widely recognized as the other SMTP ports, but it serves a crucial role for users facing specific network restrictionsList of common SMTP ports
Different Ports for Different Purposes
Each SMTP port has a specific role. For instance, Port 25 is used for server-to-server communication, while Port 587 is designed for client-to-server submissions with added security through TLS encryption. Understanding these differences helps organizations customize their email setup to meet both operational and security needs.
If you’re encountering SMTP errors, understanding the right port and its application can help troubleshoot and resolve issues more efficiently. For more information on solving common SMTP errors, check out our detailed guide here.
How Email Deliverability Is Affected by SMTP Port Selection
Choosing the right SMTP port is crucial for email deliverability. Ports like 587 and 2525 are preferred for outbound emails because they secure client submissions and are less likely to be blocked by ISPs. Using these ports helps ensure your emails reach recipients securely and boosts deliverability, protecting your sender reputation.
Comparing Security Features Across SMTP Ports
Security plays a key role in choosing an SMTP port. Port 587 uses STARTTLS to upgrade an insecure connection to a secure one, while Port 465 provides encryption from the start with SSL/TLS. Port 587 offers flexibility with encryption upgrades, while Port 465 ensures all connections are secure from the beginning. Understanding these features helps you choose the best option for your security and compliance needs.
The Future of SMTP Ports: What’s Changing?
Illustration of the future of SMTP ports
As digital communication evolves, so do the protocols that ensure secure and efficient email transmission. Emerging technologies, growing security concerns, and changing regulations are shaping the future of SMTP ports, influencing how emails will be sent and received.
Embracing Enhanced Security Protocols
Illustration of enhanced security protocols
Security remains a top concern in digital communications. As cyber threats and data breaches rise, security protocols for SMTP ports will keep improving. Future updates will likely focus on stronger encryption and tighter authentication processes to ensure secure email transmissions. We can expect newer versions of Transport Layer Security (TLS) and additional security layers like DMARC (Domain-based Message Authentication, Reporting, and Conformance) to become standard.
Shifts in Port Utilization
Port 25 is no longer widely used for client-to-server email submissions due to security vulnerabilities, but it still serves server-to-server communications. As more secure alternatives like Port 587 gain adoption, Port 25 may eventually be phased out. With ISPs tightening restrictions on traditional ports, alternative ports like Port 2525 may become more common.
Regulatory and Compliance Changes
With global data protection laws tightening, email transmission through secure SMTP ports is becoming more critical. In regions with strict regulations, emails may need to be sent through ports that support higher security protocols to ensure compliance and data privacy.
Technological Innovations
As technology advances, new or modified SMTP ports could emerge to meet specific needs or improve performance. Innovations in network technology might lead to more efficient and secure ways of sending emails, potentially changing how SMTP ports are used.
For more in-depth articles on the technical aspects of email marketing, click here to continue reading.
Frequently Asked Questions
Which SMTP Ports Can You Use at Amazon SES? At Amazon SES (Simple Email Service), you can use several SMTP ports depending on your security requirements and network restrictions. The supported SMTP ports for Amazon SES are: Port 25, Port 465, Port 587. Which SMTP Ports Can You Use at Mailgun? At Mailgun, you have the flexibility to choose from several SMTP ports to accommodate different security and delivery requirements. The SMTP ports supported by Mailgun are: Port 587, Port 465, Port 25. Which SMTP Ports Can You Use at Sendgrid? SendGrid supports several SMTP ports to cater to different security preferences and email sending needs. The SMTP ports you can use at SendGrid are: Port 587, Port 465, Port 2525. Which SMTP Ports Can You Use at PowerMTA? At PowerMTA, you can configure a variety of SMTP ports depending on your operational requirements and security policies. The commonly used SMTP ports in PowerMTA are: Port 25, Port 587, Port 2525. Is port 25 safe? Port 25 is not considered safe for sending emails directly from email clients to mail servers due to its susceptibility to spam and security vulnerabilities. What is the difference between port 587 and 465? Port 587 is recommended for sending emails securely and is commonly used as the default mail submission port. It supports STARTTLS, which is a protocol command used to upgrade an existing insecure connection to a secure connection using TLS encryption. Port 465 was originally designed for SMTPS (SMTP over SSL), which provides a secure connection from the beginning of the email transmission. Unlike Port 587 that upgrades to a secure connection using STARTTLS, Port 465 starts with an SSL/TLS encrypted connection immediately upon connecting.