In part one of How to Troubleshoot SMTP Errors, we reviewed email status codes, internal reasons for email issues, and troubleshooting steps to address those issues. In part two of this series, we will examine some of the external reasons for email issues.
External Reasons for Email Issues
After we have tested the local server and see the local server is working correctly, we can infer that the issue lies with one of the following external problems:
The Simple Mail Transfer Protocol (SMTP) is a communication protocol used to transmit email between corresponding email servers. Using an email client like Mac Mail, Outlook, Thunderbird, or web clients like Gmail or Windows Live, SMTP can send messages to an email server. Although SMTP was initially designed as an email transport and delivery system, it later encompassed the email submission protocols that are now in use by both the Post Office Protocol (POP) and the Internet Message Access Protocol (IMAP). The above-noted email clients use these protocols to retrieve email from an email server. When this system fails, it provides the means to identify and resolve SMTP errors.
First, let’s define what a port is. According to the IEFT, a port is:
“A logical entity for Internet communication. Ports serve two main purposes: 1. They provide a demultiplexing identifier to separate transport sessions between the same pair of endpoints 2. They may also identify the application protocol and associated service to which processes connect.”
In plain English, this simply means that a port is an endpoint through which data flows back and forth between two computers over a network. A computer has 65535 ports available to share information. These port numbers are based on a 16-bit number, which is where we derive the total number of available ports (0 to 65535).
One of the most common email issues we encounter is customers who are traveling and encounter problems trying to send an email. This is often the result of connecting to a new network that hasn’t been used to send email before, as an open wireless network in a coffee shop, library, or other public location. Every network has rules, and in some cases, networks have rules about what outbound email servers (SMTP) you can connect to and use.