Understanding which SMTP port to use for your email campaigns

Are finding that your emails still end up in the spam folder? Sales outreach and marketing professionals frequently struggle with this issue. While there may be many factors at play, it can often be traced back to the configuration of their email service provider, particularly the SMTP port (Simple Mail Transfer Protocol) settings. 

SMTP is the protocol responsible for sending emails, and the port you use can have a significant impact on whether your messages reach the inbox or get flagged as spam. 

In this article, we’ll break down everything you need to know about SMTP ports, including how they work, the differences between the common ports, and how to choose the best one for your needs.

Here are the key topics we cover in this article:

• What is SMTP?
• Understanding SMTP Ports
• Common SMTP Ports
• Choosing the Best SMTP Server
• Security Considerations
• Troubleshooting Common SMTP Port Issues

What is SMTP?

SMTP, or Simple Mail Transfer Protocol, is the backbone of email communication. When you send an email, SMTP is the protocol that handles the transmission of your message from your email service provider (like Outlook or Gmail) to the recipient's email server. It ensures that your email is correctly routed, delivered, and, in most cases, stored securely until the recipient opens it.

SMTP has undergone several updates to adapt to the growing demands of the internet. Today, it’s a critical component of any email marketing campaign, ensuring that your messages reach your audience. However, getting the SMTP configuration right can seem tricky, especially when it comes to choosing the right port for sending your emails. But don’t worry, we’re going to break it down for you so you can ensure your email port settings are correctly set.

Understanding SMTP Ports

To put it simply, a port is like a doorway through which information passes between your computer and another server. Each port is associated with a specific protocol or service, and when it comes to sending emails, certain ports are designated for SMTP traffic.

Different ports serve different purposes in SMTP communication. Some are designed for secure email transmissions only, while others may be blocked by internet service providers (ISPs) to prevent spam. Choosing the wrong port can result in your emails being undelivered or marked as spam, which can negatively impact your sales and marketing efforts.

The concept of default ports is also essential to understand. Default ports are those commonly used by specific protocols and services, making them widely recognized and supported. However, they also come with risks, as they are often targeted by bad actors looking to exploit vulnerabilities.

Common SMTP Ports

Port 25: The OG SMTP Port

Port 25 is the original and most widely recognized port for SMTP. Historically, it has been the default port for sending emails between servers. However, due to its age and widespread use, Port 25 has become a target for spammers. As a result, many ISPs now block this port for outgoing mail to prevent spam from being sent over their networks.

Despite its limitations, Port 25 is still used for server-to-server communication. 

If your emails are consistently being marked as spam, it could be because you're using Port 25, and switching to a different port may help improve deliverability.

Port 587: The recommended Port

Port 587 is the most up-to-date and recommended port for sending emails. Known as the submission port, it’s designed to handle email transmissions from clients (like email marketing tools) to mail servers. Unlike Port 25, Port 587 supports encryption, which ensures that your emails are transmitted securely.

Using Port 587 offers several advantages, including better compatibility with modern email systems and improved security. It’s considered the best practice for sending emails, especially for businesses and marketing professionals who want to ensure their messages reach their audience safely.

Port 465: The deprecated SSL Port

Port 465 was initially designated as the port for SMTP traffic secured by SSL (Secure Sockets Layer). However, it was later deprecated in favor of Port 587, which offers more flexibility with encryption protocols. Despite this, some email service providers still support Port 465 for legacy reasons.

While it’s not recommended to use Port 465 for new email setups, if you’re working with an older system that requires it, make sure to check whether your email provider still supports SSL encryption on this port. If not, you should consider upgrading to a more secure option like Port 587.

Port 2525: An alternative SMTP Port

Port 2525 is an alternative SMTP port that’s gaining popularity, especially among cloud-based email providers. It’s not a standard port in the official sense, but it’s supported by many email services as an alternative to Port 587. One of the benefits of using Port 2525 is that it’s less likely to be blocked by ISPs, making it a good fallback option if you encounter issues with the other ports.

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Choosing the Best SMTP Server

When selecting an SMTP server and port, several factors come into play. First, consider the volume of emails you send. If you're sending high volumes, you'll want to choose a reliable SMTP server that can handle the traffic and offers strong deliverability rates. Additionally, the nature of your emails (e.g., transactional vs. marketing) might influence your decision.

For personal use or for small businesses, a basic email service provider with support for Port 587 should suffice. However, for larger organizations or those running extensive marketing campaigns, it's worth investing in a dedicated SMTP server with robust security features.

Some of the best SMTP servers include SendGrid, Amazon SES, and Mailgun, all of which offer flexible port options and strong reputations for deliverability. It’s important to note that some SMTP servers, like Amazon SES will require some more technical setup and coding, so make sure to get input and support from your development team when choosing the best server to meet your email outreach needs.

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Security Considerations

Security is a critical aspect of email communication. Ensuring that your emails are encrypted is essential to protect sensitive information and maintain the trust of your recipients. Ports like 587 and 2525 support TLS (Transport Layer Security) encryption, which is practically a pre-requisite for sending emails and not having this security layer will affect your domain reputation. You can monitor encryption details using tools such as Google Postmaster to check inbound and outbound email traffic.

Using outdated ports like 25 or 465 without encryption can leave your emails vulnerable to hijacking, which could compromise your data and reputation. Always prioritize security when configuring your SMTP settings.

Troubleshooting Common SMTP Port Issues

If your emails are not being delivered or are ending up in the spam folder, the SMTP port you're using could likely be the culprit. Here are some common issues related to SMTP ports and how to troubleshoot them:

1. Blocked Port: Some ISPs block certain ports, like Port 25, to prevent spam. If you're experiencing issues, try switching to Port 587 or 2525.

2. Incorrect Configuration: Double-check your SMTP settings to ensure that the correct port is selected and that encryption is enabled if required.

3. ISP Restrictions: Some ISPs impose restrictions on email sending. If you're having trouble, reach out to your ISP to see if they have any port recommendations or limitations.

Tools like Mailchimp, for example, have documentation to help you troubleshoot your SMTP integration.

Choosing the right SMTP port is crucial for successful email communication. Whether you're sending marketing emails, transactional messages, or personal correspondence, the port you use can affect both deliverability and security. 

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Here is a quick round-up of the different ports and how to move forward: 

• Port 587 is the recommended port for email marketing due to its support for encryption and broad compatibility with modern email systems
• While you can use Port 25, it's generally not recommended due to its limitations and the fact that many ISPs block it to prevent spam
• Port 465 is deprecated and no longer recommended for new email setups 
• Port 2525 is a great alternative to port 587, and is less likely to be blocked by ISPs

Overall, Port 587 offers better security and compatibility and is your best bet for email outreach. 

If you’ve adjusted your SMPT port settings and you are still struggling with email deliverability and getting your emails out of the spam folder, there may be other factors affecting your email strategy. 

Book a free audit call with Allegrow to see how you can improve your sender reputation and inbox placement today

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