Can you provide me with some background about how Internet email works?

Sure! We'd be happy to! The following are a few simple yet critical concepts that you, as an Internet (and email) user, should know. We've done our best to give simple explanations so even new users can gain an understanding and become a much more effective Internet email user.

• the email software that you use on your PC desktop, e.g. Microsoft Outlook, is called a client.
• an email client lets you compose your message, and then send it to a computer (i.e. a host), running mail server software (i.e. a server). Such a host is often called a server computer, server host, or simply a server. While it can be confusing, usually the context should make it clear whether the author means the software, the host (i.e. the computer - hardware) or both.
• the server is responsible for delivering your messages to their intended recipients. The client (e.g. Microsoft Outlook) is not involved in the delivery effort.
• in general, any computer that sends a message to a mail server is usually called a client as well. For instance, even to your PC, your ISP's mail server computer is a server, but when the said server sends your message to another mail server, your ISP's server becomes the client.
• the action of "delivery" of messages, carried out by the server software, is also termed as a "relay".
• your email client may also retrieve messages that others sent to you from a server, so that you can review them and optionally reply to some of them.
• the server that takes in your messages to others (i.e your outgoing messages) is often called the SMTP server, owing to the fact that the server software uses the Simple Mail Transfer Protocol. A protocol is the way computer software (client and server) communicate with each other to accomplish a specific task (in this case, transfer a message composed by you from your client to the server).
• the server that your email client retrieves messages that others send to you (i.e. incoming) is often called POP server, owing to the fact that the server software uses the Post Office Protocol to communicate with an email client (e.g. yours). The task here is to transfer a message from the server host's storage (e.g. hard drives) to your email client.
• SMTP and POP are two independent protocols. As a result a host could run just a SMTP server, a POP server, or both.
• the SMTP, as it was designed, doesn't have any built-in authentication mechanism. By default, a SMTP server accepts any connections from any clients. In other words, it's an "open relay" since the server is "open" to any clients. These can be used by anyone (including, regrettably, spammers), located anywhere on the Internet. They all can use the host to send outgoing messages (i.e. to relay), unless some restrictions (not part of SMTP!) are applied.
• on the other hand, a POP server won't allow a client to retrieve any messages unless an authentication (i.e. login) is successful.

If you have read this far, our compliments! As we said before, your newly gained knowledge of Internet email will soon make you a much more effective user! Remember, knowledge is power.

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