How email works

with thanks to wikipedia where I stole a lot of this from.

e-mail stands fairly obviously for electronic mail annd is a dam fine method of communication. It is rapidly replacing paper letters and probably will in my lifetime.

How Internet e-mail works
A few things work together to get an email from your computer to its destination.
Sending an email
The process starts with you composing an email in a piece of (client) software often Outlook or Hotmail. When you have finished writing you press send. The message is sent using a protocol called SMTP (Simple Message Transfer Protocol) to your ISP's mail server. This is a computer that probably just deals with email traffic. The mail server has a look at the email address based on the bit of the address after the @. The mail server then sends it on to the correct mail server for that address. The send process stops here.

Receiving an email
It is important to understand that unlike a coventialnal letter which completes its journey at the address on it. Email will not get any further than your ISP's email server unless you or your computer does something about it.
There are two (nearly three) main ways of viewing your email once its has gt to your mail server.

Post Office Protocol)
If your email is set up this way (you will still be using a mail client like outlook or thunderbird as before). You download the mail maessage and any attachments from your ISP's mail server and you then read the email.
The disadvantage of this is that if you have a lot of mesages you usually have to download them all first before you can read them. On the upside you do have a physical copy of the message so if your ISP gets hacked or crashes you won't lose all your messages.

IMAP Internet Message Access Protocol.
If you use this system (you will still be using a mail client like outlook or thunderbird as before). You don't download the emails your mail client just works as a viewer and you look at the emails on the mail server.
THis is obviously quicker. Any attachements you can download seperately to your machine and you can then decide whether to keep a message on the server or delete it. Depending on the arrangement you have with your ISP you will get so much space on their server and you may have to delete some messages monthly or annually.

This is the way Hotmail and Gmail work. It is very similar to IMAP in that he messages stay on the server (which is owned by microsoft or google in this case) but this time you look at the message via a web browser. The advantages of this system are that as a web browser is now on most machines on earth you can get your mail from anywhere you can get online.

Where we are now
Quite a lot of ISP's now over a mix of all three types so the distinctions are becoming blurred. I a sperate email provider ( as I switch ISP often don't want to have to keep changing my email address and get all three services.

How intranet email Works

Just about the same is the answer. If the email address contains the name of the local (inside the intranet) mail server, the mail message stays on the server ready to be received by the person it is addressed to. If it is addressed for a mail server on the internet off it goes to your lisp's server and then on to the server on the address. In this case the email passes through three servers on its way but otherwise its the same.

Email Pros and cons