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Not all email is created equal: an introduction to POP3, IMAP4 and MAPI

by John Carthy on August 2, 2007

I was at HostingCon in Chicago last week and I heard someone comment about whether email was still the killer app.

Besides being a slightly useless thing to say, it occurred to me that email never was a killer app. A text message is a message.Rather it’s the tools used to manage messaging in combination with the protocol that makes for the better experience.

Truth is a lot of people I speak to don’t understand the difference between POP3 email, IMAP4 email and MAPI services. As a result, they don’t understand why Microsoft Exchange is so expensive (Microsoft Exchange email is based on MAPI) and so useful.

Let’s start with POP3. That’s the basic email that comes with most website hosting plans or is provided by your ISP or cable company. The most important thing to understand about POP3 is that your messages are stored on the email server until you access them through a common POP3 client like Outlook, Outlook Express or Eudora.

When you connect to your POP3 email account through one of these clients, all your unread email messages are downloaded to your local machine for you to read. They are removed from the server.

The one exception is checking your POP3 accounts through the email retrieval application ( This webmail application allows you to preview your messages, on almost any remote mail server , before they’ve been downloaded.

We get a lot of complaints from users who think we’ve deleted their emails. What actually happened was someone opened Outlook on their desktop and downloaded all their messages off a POP3 server.  Now those messages reside in someone’s office / home PC and can’t be easily accessed.

IMAP4 is different in that email is stored on the server. There is an added bonus of being able to create folders to manage your messages. When you connect to an IMAP4 account, the messages are not downloaded to your local computer but instead are previewed for you, recording what has been read and what hasn’t and allowing you to move messages to folders you created.

This is important as IMAP4 accounts give you the ability to access your email from multiple locations and computers and maintain a synchronized copy.

Apple's Iphone - supported by's email as well as MS Exchange All the email accounts provided with hosting plans on are both POP3 and IMAP4 compatible. Apple’s iPhone uses the IMAP4 protocol for email syncronization which you can use with our Exchange hosting plans or our email acccounts.

But the killer app is Microsoft Exchange based on the MAPI protocol. Okay,  I hate the term killer app . . . but it’s the best messaging platform on the market. MAPI is an aware protocol and by that I mean it is constantly listening for changes on the server and then communicates those changes to you, however you are connected (browser, desktop, mobile device). If you are running Outlook with a full Exchange account (our Professional account) you don’t have to constantly click send and receive to see if you have new messages. Changes are pushed as they are recorded on the server.

Like IMAP4, all messages are stored on the server but Exchange also stores your calendar, contact, journal, tasks and much more. All this data is aware of changes and communicates those changes immediately. You can also share real-time data with others in your organization and collaborate in a way you could never do with POP3 or IMAP.

Of course all this enhanced functionality requires extensive hardware to support. While diskspace costs have gone down considerable in the past 5 years, even the best SCSI drives have a maximum rate at which they can read or write data.

Exchange hits this maximum quickly with very few active users. And that’s just one of the reasons why Microsoft Exchange is so much more expensive than POP3. Microsoft’s monthly license fees – charged directly to Exchange hosters - also adds to our costs.

But it’s still much less than what your business pays for phone service and in my opinion, just as important and effective for running an efficient business.

John Carthy
V.P. of Sales and the Marketing
SoftCom Technology Consulting Inc.

Related posts:

  1. Video Tutorial: How To Set Up a POP3/IMAP4 Exchange Account
  2. Hosted Exchange vs. Email: Elevate your Experience
  3. iPhone 3G and Email Integration Options incl. Free Exchange Account
  4. What does your email address tell people about you?
  5. Hosted Exchange Email now available from


jw August 24, 2007 at 7:48 PM

You don’t mention, but while most email client software defaults to downloading POP3 email and deleting it from the server, most allow you to set to download without deleting.

r4 sdhc September 26, 2009 at 6:14 AM

I knew about POP3 and IMAP4. But what is this MAPI? searched it on net but could not get it. Please explain. provide more information and links to related topics. Thank you.

Tim Attwood September 28, 2009 at 10:13 AM

Hi There,

MAPI is the connection that Outlook makes to the Exchange server to view and synchronize your Exchange data.

Stoddard September 22, 2010 at 8:44 AM

I agree that Microsoft Exchange based on the MAPI protocol was from the start a killer app…or whatever you want to call it.

PotsNPans January 4, 2011 at 11:27 AM

I think Exchange is becoming more important than phones service, especially as VOIP begins to rise.

Rusher February 21, 2011 at 3:29 PM

It’s great to be able to have a synchronized copy–one of the real selling points of IMAP4.

WrigleyF April 13, 2011 at 6:57 AM

I agree with you about Exchange. I wish it were cheaper, but the benefits in the end outweigh the costs.

Texas2Step August 17, 2011 at 9:55 AM

The wiki article on MAPI was great to read; I’d also been wondering what it was, and this technology fascinates me.

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