Crabby demystifies e-mail protocols

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Let's talk about what an e-mail "protocol" is, what the most popular types are, and why you should care. We're taking this one step at a time, so no panicking.

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I get a bucketload of mail dropped off in my office every day and a surprising amount of it asks me to discuss the differences between POP3, IMAP, and HTTP mail. (Really!) And because I do listen to you, I've devoted an entire column to the word "protocol." (Be careful what you wish for, I guess.)

Warning    There are going to be more than the usual amount of acronyms bandied about in this column. This isn't my fault; I didn't make them up. I'm just here to help you get through them. So now, as my dentist likes to say, "You may feel a slight pinch..."

Protocol: A code of conduct and the conduct of code

Usually when I hear the word "protocol," what comes to my mind are mustachioed men and white-gloved women speaking tactfully and in multiple languages at a head-of-state dinner party. Typically, the word means "rules or conventions of correct behavior on official or ceremonial occasions." (Thank you, MSN Encarta dictionary.)

While we're not talking about diplomacy (not really my specialty, as you might imagine), let's just say there are similarities between the ceremony and etiquette diplomats specialize in and the mechanics behind e-mail. Confused already? Okay, when we talk about an e-mail protocol, we're talking about an agreed-upon format for sending and receiving e-mail messages. And, when you think about it, this is kind of like ceremony and etiquette for how to get your e-mail messages out there.

Now that that's as clear as mud, why should you care? You should care because unless you know what protocol your e-mail provider supports, you won't be sure about how to set up Outlook, Outlook Express, Windows Mail, or any other e-mail program. And then you won't be able to get your e-mail, and then where will you be?

So... let's go over the various types of protocols you can use. Note that some e-mail hosts support all kinds and some don't. I'll give you a few examples, but you'll need to contact your provider to find out what exactly they offer.


When you use the very common Post Office Protocol 3 (POP3), your e-mail is stored on your e-mail provider's server initially. But once you go and "get it" from Outlook, Outlook Express, or whatever e-mail program you use, it's downloaded to your computer and is no longer stored on the server. If you want to keep it, you have two choices: never delete it from your program, or create a copy of it and keep it somewhere on your computer. (I'm sure you're better at remembering where you put it than I am.)

Use the POP3 protocol when:

  • You have one computer and want to store all your mail on that computer.

  • Security is a concern — you don't want your messages stored on an external server (like with IMAP and HTTP mail, which we'll get to in a minute).

  • You don't want to have to be connected to the Internet to be able to read e-mail.

  • Your e-mail provider doesn't support any other kind of protocol.

Note   Some POP3 e-mail providers have special Web sites set up so you can access your e-mail from anywhere. This, however, is not the same as IMAP or HTTP mail.


Internet Message Access Protocol (IMAP) is a way to access your e-mail on a server and, if you like, keep your e-mail messages stored there instead of on your local computer. An example of a service that uses IMAP mail is Gmail.

Use IMAP when:

  • You have multiple computers and you want to be able to access your e-mail from any one of them (and the Web).

  • You want to view just the headers of your e-mail messages and decide whether you want to download them. No need to download an entire spam message when the heading is shocking enough.

  • You want to create and move folders or mailboxes, delete messages, and even perform a search for certain parts of a message — all on the server.

  • You don't mind being connected to the server (and, necessarily, the Internet) continually while you're receiving or sending your e-mail.

Note   While this is all well and good, not all e-mail providers support IMAP. So before you get all excited, I'd check with them.


Hypertext Transfer Protocol (HTTP) is used to display Web pages, but it can also be used to send and receive e-mail.

You'll be using HTTP mail when:

  • You have an account with Windows Live Hotmail, Yahoo!, or any other Web-based e-mail service. You can read and receive e-mail messages from any computer in the world with an Internet connection and a Web browser that supports graphics.

  • You're using Microsoft Exchange Server and Microsoft Outlook Web Access (OWA). With OWA you can get all your mail, contacts, and calendar information on the server by using an Internet browser from a UNIX, Macintosh, or Windows-based computer.

  • For remote connections, you can also use HTTP to connect from Outlook 2007 or 2003 to a Microsoft Exchange Server 2007 or 2003 using a feature called "RPC over HTTP" (sexy name, isn't it?). This is an alternative to the standard VPN (virtual private network) connection. Read more about how to use Outlook anywhere to connect to your Exchange server without VPN.

Note   HTTP accounts are also not as private as POP3 accounts since your messages are stored on an external server. Also, the amount of space you get to store messages is limited; if you go over that set amount you won't be able to get or send more messages until you clean your room.


Messaging Application Programming Interface (MAPI) is used with Outlook in conjunction with a Microsoft Exchange Server mail server. MAPI is a lot like IMAP (in fact, it's an anagram of it), but it provides a wider array of features when you use it from within Outlook. In fact, MAPI makes it possible for other Office programs (such as Microsoft Word and Microsoft Excel) to work with your e-mail program.

Note   When you are using MAPI, it serves as both your incoming and outgoing mail server.

Use MAPI when:

  • You want to develop new types of custom forms.

  • You need your e-mail program (such as Outlook) to work with another program (such as Word). For example, maybe you want to access your Outlook Contacts folder for a mail merge you're setting up in Word.

  • You want to use profiles to configure how an e-mail message is transmitted and where it is stored.

  • Your organization uses Outlook with Exchange Sever so you have no choice in the matter.

SMTP (Simple Mail Transfer Protocol)

Most (but not all) e-mail systems use SMTP to send e-mail messages across the Internet from an e-mail client to an e-mail server. (As mentioned above, MAPI functions as both the incoming and outgoing mail server.) That's why you need to specify both the incoming server (POP3, IMAP, and so on) and the outgoing server (the SMTP server) when you set up your e-mail accounts.

Before you dash off to configure your account... sure to contact your e-mail provider and find out what protocols it supports. Then think about how you use e-mail, how much you use it, and from where you want to access your mail:

  • If you're using Windows Live Hotmail or Yahoo!, that's HTTP mail. You can access these types of mail accounts mail from either a Web browser or Outlook. Talk about convenience!

  • Use a Windows Live Hotmail account in Outlook

  • If you need a lot of cooperation between your e-mail client and other programs (such as Word, PowerPoint, or OneNote), MAPI is the protocol for you.

  • If you use Outlook 2007, 2003, or 2002, you can configure it to receive messages from your Exchange Server account, a POP3 account, and an HTTP account. Oh, the gluttony of it all.

See? That didn't hurt a bit and I didn't even have to numb you (much).

"A diplomat's life is made up of three ingredients: protocol, Geritol , and alcohol." — Adlai E. Stevenson

About the author

Annik Stahl, the Crabby Office Lady columnist, takes all of your complaints, compliments, and knee-jerk reactions to heart. Therefore, she graciously asks that you let her know whether this column was useful to you — or not — by entering your feedback using the Was this information helpful? tool below. And remember: If you don't vote, you can't complain.

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Applies To: Outlook 2007, Outlook 2010

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