Email Basics Explained

What are email protocols?

Whenever one speaks about email the word "protocol" comes up. This is a language that computers use to talk to each other. To understand email we need to know what these protocols are and the basics how they work. This will make it so much easier to solve any problem regarding email.

What email protocols exist?

  • POP (Post Office Protocol): POP is the old protocol used for fetching mail to your mail client.
  • IMAP (Internet Message Access Protocol): IMAP is like POP for fetching mail. But when you use IMAP then the mail stays on the server.
  • SMTP (Simple Mail Transfer Protocol): SMPT is for sending mail out.
  • Exchange from Microsoft: Exchange is both for sending and receiving mail. But Microsoft being Microsoft everything is a bit special.
  • Gmail: Google can speak POP, IMAP, SMTP and Exchange. While Microsoft designs a completely new protocol Google uses the existing ones but in their style. This is why differences - especially in IMAP - will be explained in a separate section.

Which protocols do you use?

Except for Exchange you always use a combination of protocols. Whenever you send a message to someone you HAVE to use the the SMTP protocols. This needs an SMTP server with username and password. When you get messages then you can use either POP or IMAP. These also need a server with username and password. The server names will be different, but username and password are almost always the same.

What is POP?

New mails are downloaded from the POP server to the mail client. The client can tell the server to delete the messages. Mails are always downloaded to the Inbox. The server doesn't know anything about if the message is read or unread. The intent of POP is to have one main mail client that is used to interact with the mail.

What are the benefits of POP?

It's old and simple.

What are drawbacks of POP?

POP is really old. Nobody has only one computer anymore. I want to read mails in the office, at home, on my mobile, during holiday (not really). Even if I leave the messages on the server with POP I need to have a mailbox structure and I need to know which message are already read. This was the reason for the creation of IMAP.

What is IMAP?

When you use IMAP then the mails will stay at the server even if they are downloaded to a computer. Any change you make locally to a mailbox of an IMAP account is reflected back to the server and then is changed in any other mail client that also uses this IMAP account. You continue to work normally within your email client. But if your motherboard goes kaputt like mine did in the summer 2012 then you just enter your username/password/servers combination into your other computer and everything is as it was before. You can even edit/view/delete your mails in the browser of your choice.

And what about iCloud?

The mail part of iCloud uses the IMAP protocol.

What are the benefits of IMAP?

Your mails can be accessed from different computers and all have the same data.

What are drawbacks of IMAP?

IMAP is a bit more complicated than POP and of course nothing is perfect. So read about the drawbacks and decide which are important to you.

  • Quotas: Space on a server is always expensive. If you get many mails quota space may fill up very fast.
  • Because the IMAP protocol is a bit more complicated there are some variations in the wild - notably Gmail.
  • If someone hacks your account and you haven't downloaded your email to your computer, then the mails are gone. As with every other kind of data it's your job to do due diligence.

What is Exchange?

Microsoft Exchange offers email, contacts, shared calendars and other functionality. On the Windows side Outlook is the application for Exchange. On the Mac side Entourage/Outlook and Mail can access Exchange servers. AppleMail only supports Exchange mail. Exchange comes in different flavors - in Microsoft style in year versions. There are currently versions 2007, 2010 and 2013. Under the hood Exchange can use POP, IMAP, and SMTP. In 10.5 Leopard Mail could talk to Exchange servers only via IMAP and SMTP. Snow Leopard added native support to talk to an Exchange server directly. Lion added support for Exchange 2010. Version 2013 is quite new.

Benefits of Exchange

Exchange is supposed to be a robust implementation of email protocols for businesses of all sizes. There is no reason to use this in a private environment. For an Exchange user the handling is almost like with IMAP. Like IMAP the mails are stored on the server and any local change is reflected back to the server.

Drawbacks of Exchange

Exchange accounts can only be accessed by Mail and Entourage/Outlook on the desktop. iPad and iPhone can access Exchange accounts, too, but don't have push notifications. This means that you need to wait for the next scheduled download of the mails or you need to do get mails manually.

What are the differences of Gmail?

Gmails can be accessed via IMAP or POP if you use a mail client. POP doesn't make much sense as explained above.


The browser based Gmail has Labels. Each mail can be labeled with multiple labels. This solves the age-old problem when a mail belongs to multiple categories. This doesn't fit to the Imap mailboxes where a mail can belong to only one mailbox. Even the Inbox is a Label. As a result mails can be downloaded once for each Label applied to it.

Gmail's Archival

Gmail has a quite different archival concept. Archiving Gmail style just removes all Labels from a message which removes it from all mailboxes.

Benefits of Gmail

It doesn't cost anything. The storage capacity is good.

Drawbacks of Gmail

You get obnoxious advertisements when viewing Gmail via browser. Nobody has any clue what Google does with your email data. The concepts of Gmail don't fit 100% to the Imap ones. As a result mail may be downloaded multiple times to the computer.

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