How does email work – in simple words

We all use email every day, but most of us take it for granted without knowing how it actually works. There’s some pretty strange terminology around this subject – let me explain it to you in simple words.

Your Local Email Client

First let’s talk about the email client. That’s the programme you use to check your emails. Outlook is an email client, so is Thunderbird, Mail on Mac, Outlook Express, and even the app you use on your smart phone which you can read and send emails with. Many email services also provide access via a web interface in your browser, those are called Webmail Clients – and they’re also email clients.

Whenever you hear someone ask “what is you email client?” then what they mean is “which thing is it you’re using to read your email”.

The Incoming Mail Server

Your computer isn’t always on, so in order for you to be able to receive email at any time of the day, there’s a server somewhere in the depths of the internet which is switched on all the time. He’s listening to emails that are sent to your address – and if one arrives he puts it into a folder on his system, waiting for you to check your emails.

This guy is called your Incoming Mail Server and he’s usually working 24/7 without holidays. This server is maintained by your email provider and he can do one of two things:

Either he saves an email addressed to you and waits for you to check your email, or he can forward each email to a different address. This is useful if you have several email accounts but you’d like to receive all your mail in another central account.

If the mail server doesn’t know the address that he receives an email for, or there’s a problem on the system, he will send the email back with a message saying “Hey sender, I don’t know this recipient”. This is called bouncing (as in the email will bounce back to the sender).

A mail server usually takes care of thousands of mailboxes, so in order for him to know that you are you, you’ve been given an account with him – identified by a user name and password.

Checking Emails

All email clients need a few bits of information to communicate with the email server: that’s the host address (or mail server address), the user name for your account, and your password. Clever email clients know some details about your email service provider so all they need to know is your user name and password.

Typically it’s something like this:

  • Incoming Mail Server: (or
  • User Name:
  • Password: somepassword

There’s one other important element involved though: the language in which the client and the server can communicate. Your choices are POP and IMAP, cryptic abbreviations for something that sounds extremely techie.

Nowadays both are equally supported and the choice is yours. Let me explain the differences and the pros and cons.


Sometimes also called POP3 is the Post Office Protocol. It downloads all emails from the mail server and stores them in your local inbox. You have a choice of only downloading new emails that are not yet on your local system, and you also have the choice to delete emails on the mail server once they’re on your local system.

This option is good if you only have a limited amount of space on your mail server and you want to clear it out regularly. It’s also good if you access your emails from only one system.

The downside is that when you check emails from two or more devices, then only one device will have the latest emails on it which can get confusing. The same goes for sent emails – which device did you send the email from you’d like to have another look at? POP used to work really well when we all had one central system, but times have changed. Enter IMAP.


Sometimes also called IMAP4 is the Internet Message Access Protocol. It assumes that you would like to leave all your messages on the remote server and only want to synchronise your local email client with the server. So all your emails are stored in one place (i.e. on the mail server) and you tell the mail server which emails you’ve read or moved to a different folder.

When you check emails from another device, it will synchronise with the same information so you’ll see emails the same way no matter which machine you’reaccessing them from.

IMAP is the more logical choice to use as of 2012, however even though it’s great when it works, it’s an extremely complex mechanism that happens on the mail server’s end. You’ll also want a lot of storage on your mail server. If your server and your email clients support this option, always go for IMAP. If not, you’ll have to live with POP.

The Outgoing Mail Server

We’ve spoken about the incoming mail server already (it’s the guy that receives your email while you’re asleep), but if you’re sending emails out then often his friend will take of this job: the outgoing mail server. Technically this can be handled by the same physical server, but in larger systems those will be two different machines.

The outgoing mail server communicates in a different language than the incoming server, namely SMTP (which is the Simple Mail Transfer Protocol). You’ll sometimes see this as an option in your email client.

Since these can be different machines, you may be given different information by your email service provider, typically like this:

  • Outgoing Mail Server:
  • User Name:
  • Password: somepassword

Outgoing mail isn’t more complex than incoming mail, but sadly extra security measures have been put in place because of the amount of spam email that gets sent every day. Spammers like using harmless outgoing mail servers and bombard them with milions of messages which bogs down the machines that want to send them out.

Therefore, email providers have put extra checks in place which means you may have to authenticate that you’re you before you can send your mails out. It depends on the service provider’s policy though and they’ll usually give you details on how to setup your client.

Email Adresses: Forwards and Aliases

Lastly, when you have an email account with an email provider, you’ve been given am email address like That’s usually associated with your mail account.

But what happens if you’d also like to have, as well as Do you have to have separate accounts for those?

No you don’t, you can do two things: either these emails can be forwarded so your emails will ultimately end up with, or you can have Email Aliases.

Aliases tell the incoming mail server that “if something for firstname.lastname comes in, treat it as if it were for lizzy”. It’s just an instruction really to tell the server how to handle a request, a bit like an “if… then” statement.

That about covers it all – now you know all there is to know about how email works 😉

I hope it all makes sense, feel free to ask a question below if anything is unlcear.