Internet Standard Simple Mail Transfer Protocol

SMTP Basics

In layman’s terms, the Internet standard Simple Mail Transfer Protocol (SMTP) can be described as a post office, of sorts, in that it is used to process and distribute electronic mail. Now that you are envisioning a virtual post office, think of SMTP servers as the actual postal workers. These servers are responsible for transferring your message to the intended recipient, and sending it back to you if there was a problem. To get a better idea of how this process works, try looking at the headers from an email message that was bounced back to you (e.g., you accidentally misspelled the recipient’s email address). You will find a time-stamped record of the conversation the corresponding servers had immediately after you hit “send” within the headers.

How a SMTP server communicates with other servers

SMTP servers “talk” to each other via Transmission Control Protocol (TCP/IP) ports. You can think of these virtual ports as telephones. This is how the email client and server exchange information, and the ports are numbered accordingly. The most commonly used TCP port number is 25. The SMTP servers, after they are connected by the ports, communicate by breaking down data sent from your computer into what are called packets. These packets consist of commands and reply codes. Some of the typical commands and reply codes, as well as what they stand for, are as follows: Authentication (AUTH), Binary Data (BDAT), Delivery Status Notification (DSN), Hello (HELO), Verify (VRFY), Syntax error, no parameters allowed (501), Command not implemented (502), Bad sequence of commands (503), and Command parameter not implemented (504).

Once the data packets have been “green-lighted” by the receiving server, they, along with your outgoing email message, are then sent on to the intended email recipient’s computer. It should be noted that every SMTP server is unique in that they each have their own code. For instance, Gmail users who want to use Gmail as their SMTP server would have to properly configure both their email account as well as their client in order for that to be possible.

How SMTP relay works

SMTP relay services offered by companies such as GoDaddy allow you to use a pseudonymous email address for personal or professional reasons. For example, a Gmail account user who wants to start a blog or an online store can use GoDaddy’s SMTP relay service to send and receive email by way of a different email address. The email recipients would only see the pseudonymous blog or e-business handle (e.g., [email protected] or [email protected]) as opposed to your Gmail email address. The messages they send back to you would be sent “in care of” your blog or e-business email address, but your GoDaddy’s SMTP relay service would forward those messages to your Gmail account. Another benefit of using a SMTP relay service to process email is the fact you don’t have to create several email accounts to send and receive specific messages.

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Wayne Hemrick is familiar with all the information about SMTP relay servers and the features offered. Wayne refers to Send Grid for quality service for a discounted price.