What’s the Difference Between SMTP Ports 465 and 587?

smtp ports

In the realm of email communication, SMTP (Simple Mail Transfer Protocol) is the cornerstone that enables the seamless transmission of messages across networks. SMTP relies on ports for data transmission, and two commonly used ports are 465 and 587. These ports play a crucial role in securing and delivering your emails.

In this article, we’ll dive into the differences between SMTP ports 465 and 587, their significance, and how they impact your email communication.

Understanding SMTP Ports: A Brief Overview

SMTP ports serve as entry and exit points for email traffic between servers. They determine the path through which emails are sent, received, and authenticated. When sending an email, your email client or server connects to a specific port, allowing the server to send the message to the recipient’s email server.

SMTP Port 465: SSL/TLS-Encrypted Communication

SMTP port 465 is synonymous with secure email communication. It operates with SSL (Secure Sockets Layer) or TLS (Transport Layer Security) encryption, ensuring that the data transferred between the sender and recipient is encrypted and protected from unauthorized access. This encryption secures sensitive information such as usernames, passwords, and the email’s content.

SMTP Port 587: StartTLS-Enabled Communication

SMTP port 587, on the other hand, is designed for secure communication as well. It employs the STARTTLS command, which initiates a secure connection after the initial connection is established. This approach allows the server and client to negotiate encryption details before sending or receiving any sensitive data.

Key Differences Between SMTP Ports 465 and 587

Encryption Method:

  • SMTP Port 465: Utilizes SSL/TLS encryption to secure the entire communication channel from the beginning.
  • SMTP Port 587: Employs the STARTTLS command to initiate a secure connection after the initial connection.


  • SMTP Port 465: Authentication occurs within the encrypted connection, safeguarding credentials.
  • SMTP Port 587: Authentication happens after the STARTTLS command, preventing sensitive information exposure during the initial handshake.

Server-to-Server Communication:

  • SMTP Port 465: Traditionally used for client-to-server communication.
  • SMTP Port 587: Commonly used for server-to-server communication and submission of outgoing emails by clients.

ISP Restrictions:

  • SMTP Port 465: Some ISPs block this port due to its historical association with abuse by spammers.
  • SMTP Port 587: Often left open by ISPs as a secure alternative for email submission.


  • SMTP Port 465: Typically requires minimal configuration as it is intended for client use.
  • SMTP Port 587: Often requires additional configuration due to the STARTTLS negotiation.

Choosing the Right Port for Your Email Setup

Selecting the appropriate SMTP port depends on your email setup and requirements:

Use Port 465 When:

  • You require a direct, secure connection from your email client to the server.
  • Your email client does not support the STARTTLS command.
  • You prioritize client-side encryption and wish to reduce configuration complexity.

Use Port 587 When:

  • You need a secure connection for server-to-server communication or email submission.
  • Your email client supports STARTTLS and can negotiate secure connections.
  • You aim to ensure secure transmission of data while maintaining compatibility with modern email standards.

Summing Up!

The choice between SMTP ports 465 and 587 reflects the broader commitment to securing your email correspondence. As you embark on this journey to optimize your email communication, remember that the path to success is not one you have to navigate alone. 

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Whether you’re delving into SMTP ports or crafting impactful email campaigns, our team is dedicated to providing you with the insights and support you need. From configuring your email setup to maximizing the potential of your campaigns, we’re here to ensure that your email communication is secure, effective, and aligned with your organization’s goals.


Q1. What are SMTP ports 465 and 587?

A. SMTP (Simple Mail Transfer Protocol) ports 465 and 587 are communication channels used to send and receive emails. They play a pivotal role in securing and facilitating the transmission of emails between servers and clients.

Q2. Which port is suitable for secure client-to-server communication?

A. SMTP port 465 is ideal for secure client-to-server communication, as it offers SSL/TLS encryption right from the start. This port is particularly useful when you want to establish a secure connection without additional negotiation steps.