How email works - an Introduction

This is the cornerstone to helping yourself as an email user, or if you are an administrator - getting your users to understand how email works. When email users understand the basics of how email works, they are much more likely to avoid needing technical assistance and when they do, they tend to be much more helpful in providing the information the administrator will need to solve the problem. Please feel free to refer your organizations users to this page, or any other page in this site.

When you send an email, there are a minimum of three different computers touching that piece of data. Obviously, the senders machine first - the one used to write the email. The senders machine then sends that email to an email server which is specified when your email software was configured. From the server, the email is then delivered.

Delivery can mean a number of different things. If the email you are sending is to someone within your organization, then delivery means that the email is stored in the recipients mailbox, awaiting retrieval. This is the simplest of scenarios and encapsulates three computers - the senders, the server, the recipients.

In a more complicated scenario, there could be dozens of different servers and machines that all work together to deliver an email. Email sent from you to someone outside your organization will go to your server, through a firewall, gateway etc to another email server sitting - who knows where. From there it can make hop after hop on its way from server to server until it finally reaches its final destination server - the recipients server.

It's easy to see that email doesn't just go from one computer directly to the inbox on another persons computer. There could by many machines that touch the message along the way.

All of this traveling around is does not happen by chance. It's all controlled by a protocol named SMTP or Simple Mail Transfer Protocol. SMTP also acts to "store and forward" your email. In the event that your recipients mail server is not functioning, SMTP specifies a retry period during which delivery will be attempted multiple times a day, for several days before giving up. You've no doubt seen notifications that an email you sent two or three days ago wasn't delivered.

In the end, it's like driving a car. Buttons, knobs, and in this case - a send button, do far more work under the covers than might be apparent. On this case, a 'send' button winds up doing a great deal of work in order to deliver an email from you to your email recipient.