The text discusses the concept of SMTP ports, which are communication endpoints used for transferring email data over Simple Mail Transfer Protocol (SMTP) as it moves through a network. Different ports are reserved for different types of protocols and their associated functions. The main ports mentioned in the article are 25, 587, and 2525, each with its own use cases and recommendations. Port 587 is considered the most widely recognized and compatible port for sending email, while port 2525 is an alternative when port 587 is blocked. Understanding the correct SMTP port to use can help prevent issues with email delivery and ensure that emails are sent efficiently. The article also mentions Postmark's SMTP service as a reliable option for sending emails.