Email: What’s the Difference Between POP3, IMAP, and Exchange?

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We send a lot of email these days—at work, at home, on our phones… But do you know what all the email jargon means? Keep reading to find out more about the difference between the various ways to receive email.

Whether you use Gmail, Hotmail, Yahoo mail, or email configured on your own website—there’s more to receiving email than it might seem like on the surface. Today, we’ll be focusing on answering some of the most common stumbling blocks when it comes to setting up new email accounts and explaining the difference in clear language. For our geekier readers who already know that stuff, feel free to join in the discussion—let us know how you explain to relatives and tech-challenged coworkers the difference in common email setups… or simply share this guide and save yourself the trouble of explaining it!

Email Clients vs Webmail

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Before we explain the different protocols used to download emails, let’s take a few minutes to understand the simpler stuff—the difference between email clients and webmail. If you’ve ever started a Gmail, Hotmail, or other email account, chances are you’ve used webmail. If you work in an office and use a program like Microsoft Outlook, Windows Live Mail, or Mozilla Thunderbird to manage your emails, you’re using an email client.

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Both webmail and email clients are applications for sending and receiving email, and they use similar methods for doing this. Webmail is an application that is written to be operated over the internet through a browser, usually with no downloaded applications or additional software necessary. All of the work, so to speak, is done by remote computers (i.e. servers and machines you connect to through the Internet).

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Email clients are programs that are installed on local machines (i.e. your computer, or the computers in your office) to interact with remote email servers to download and send email to whomever you might care to. Some the back end work of sending email and all of the front end work of creating a user interface (what you look at to receive your email) is done on your computer with the installed application, rather than by your browser with instructions from the remote server. However, many webmail providers allow users to use email clients with their service—and here’s where it may start to get confusing. Let’s run through a quick example to explain the difference.

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We sign up for a new email address with Google’s Gmail and begin sending and receiving email through the webmail service. Google is providing two things for us—a web frontend, and a mail server backend for sending and receiving the emails. We communicate with the email server backend by using the webmail frontend. Through our pointing, clicking, and typing, we’re telling the email server who we want to send email to, and what we want to say.

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But, we might decide that we don’t like Google’s new look for Gmail, so we decide to switch to an email client, like the free program Thunderbird. Instead of using our web based client (Gmail’s web interface) to interact with Google’s Gmail servers (the mail server backend), we use a program installed on our computers (in this case, Thunderbird) to contact the mail server backend ourselves, and sidestep webmail altogether. Google (and other webmail providers) offer all of these products, including the web frontend and the mail server backend. You can use both of them or only the mail server backend and still be using “Gmail.” And with that confusion dispelled, let’s take a look at the common email protocols you’ll run into using email clients or mobile phones.

POP3, Post Office Protocol

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POP, or Post Office Protocol, is a way of retrieving email information that dates back to a very different Internet than we use today. Computers only had limited, low bandwidth access to remote computers, so engineers created POP in an effort to create a dead simple way to download copies of emails for offline reading, then remove those mails from the remote server. The first version of POP was created in 1984, with the POP2 revision created in early 1985.

POP3 is the current version of this particular style of email protocol, and still remains one of the most popular. Since POP3 creates local copies of emails and deletes the originals from the server, the emails are tied to that specific machine, and cannot be accessed via any webmail or any separate client on other computers. At least, not without doing a lot of email forwarding or porting around mailbox files.

While POP3 is based on an older model of offline email, there’s no reason to call it obsolete technology, as it does have its uses. POP4 has been proposed, and may be developed one day, although there’s not been much progress in several years.

IMAP, Internet Message Access Protocol

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IMAP was created in 1986, but seems to suit the modern day world of omnipresent, always-on Internet connectivity quite well. The idea was keep users from having to be tied to a single email client, giving them the ability to read their emails as if they were “in the cloud.”

Compared to POP3, IMAP allows users to log into many different email clients or webmail interfaces and view the same emails, because the emails are kept on remote email servers until the user deletes them. In a world where we now check our email on web interfaces, email clients, and on mobile phones, IMAP has become extremely popular. It isn’t without its problems, though.

Because IMAP stores emails on a remote mail server, you’ll have a limited mailbox size depending on the settings provided by the email service. If you have huge numbers of emails you want to keep, you could run into problems sending and receiving mail when your box is full. Some users sidestep this problem by making local archived copies of emails using their email client, and then deleting them from the remote server.

Microsoft Exchange, MAPI, and Exchange ActiveSync

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Microsoft began developing MAPI (sometimes called Messaging API) not long after IMAP and POP were first developed, although it has uses beyond simple email. Thoroughly comparing IMAP and POP to MAPI is pretty technical, and out of scope for many readers of this article. Simply put, MAPI is a way for applications and email clients to communicate with Microsoft Exchange servers, and is capable of IMAP style syncing of emails, contacts, calendars, and other features, all tied into local email clients or applications. This function of syncing emails is branded by Microsoft as “Exchange ActiveSync.” Depending on what device, phone, or client you use, this same technology might be called any of the three Microsoft products (Microsoft Exchange, MAPI, or Exchange ActiveSync), but will offer the same cloud-based email syncing as IMAP.

Because Exchange and MAPI are Microsoft products, only companies that own their own Exchange mail servers or use Windows Live Hotmail will be able to use Exchange. Many clients, including the default Android mail client and iPhone, are Exchange ActiveSync capable, giving Hotmail users IMAP style cloud-based email, despite Hotmail not offering true IMAP functionality.

Other Email Protocols

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Yes, there are other protocols for sending, receiving, and using email, but most of us that are using plain old free webmail and mobile phones will be using one of these three major ones. Since these three technologies cover the needs of nearly all HTG readers, we won’t be spending time today talking about the others. If you have any experience using email protocols not listed here, we’re interested to hear about it—feel free to discuss them in the comments.

In Short: Which Do I Use to Set Up My Email?

Depending on your personal style of communicating and whom you prefer to get your email service from, you can pretty quickly narrow down how you should use your email.

  • If you use check your email from a lot of devices, phones, or computers, set up your email clients to use IMAP.
  • If you use mostly webmail and want your phone or iPad to sync with your webmail, use IMAP, as well.
  • If you’re using one email client on one dedicated machine (say, in your office), you might be fine with POP3, but we’d recommend IMAP.
  • If you have a huge history of email and you’re using an old mail provider without a lot of drive space, you may want to use POP3 to keep from running out of space on the remote email server.
  • If you use Hotmail or an Exchange Server Email, MAPI or Exchange ActiveSync will give you similar cloud-based syncing, like IMAP.
  • If you don’t use Hotmail and you want email sync, use IMAP. If you do use it and want email sync, use MAPI/Exchange ActiveSync.

Hopefully that’s dispelled a lot of your questions regarding these common ways we receive email data with our phones and computers.

Image Credits: Blackberry Email by Ian Lamont, available under Creative Commons. Mail by Pacdog, available under Creative Commons. iPhone: The Home Screen by Pieter Ouwerkerk, available under creative commons. Email? by Tama Leaver, available under Creative Commons. Some screenshots and logos via Wikipedia, assumed fair use.

Eric Z Goodnight is an Illustrator and Stetson-wearing wild man. During the day, he manages IT and product development for screenprinted apparel manufacturing; by night he creates geek art posters, writes JavaScript, and records weekly podcasts about comics.