What is IMAP and How Can It Help Me Manage My Email?

Using multiple devices? You’ll want IMAP.

IMAP stands for Internet Message Access Protocol. It’s a fancy name for a protocol used by email programs like Outlook, Thunderbird, and others to access your email.

IMAP is an alternative to POP3 (Post Office Protocol 3), and it works in different ways.

I’ll examine IMAP, how it compares to POP3, and when you might want to consider using it — which is most of the time these days.

IMAP: Your messages stay on the server

The biggest single practical difference between IMAP and the older POP3 is that with IMAP, your email stays on your email service provider’s server. Think of it as the official master copy of your email.

The software you use to access your email is just a way of looking at that master repository.

IMAP: a window into your mail

Whether you set up an email program like Thunderbird (or Outlook or another email program) to access your email via IMAP or connect your phone or mobile device to your email (which typically also uses IMAP), the best way to think of what’s happening is that the program is showing you what’s on the server.

And that’s it.

At least conceptually.

IMAP: downloads

Your email program may download a copy of the email to your PC.

You’re still looking at your email as it lives on the mail server’s repository, but your email program has optimized the experience by downloading the email so you can access and display it more quickly.

You can access email downloaded by IMAP even when you’re offline if your email program is appropriately configured.

That’s more or less the same as POP3. But there is one important difference.

IMAP copies; POP3 moves

When IMAP downloads your email, it copies the email onto your computer. The original email remains in the email server’s master repository of your email. Downloading it puts a copy of it on your PC for quick and easy access. (Or backup, as we’ll see in a moment.)

When POP3 downloads your email, on the other hand, it moves the email from the email server to your PC. By default, when a download is complete, the email resides only on the PC to which it was downloaded.

This “copy, not move” difference between IMAP and POP3 enables a couple of very interesting things.

IMAP: as many devices as you like

Since using IMAP is only a “view” of the master copy of your email stored on a server, you can have more than one computer open up that view.

In fact, if you’ve got a mobile device accessing your email, you might be using IMAP already, as it’s a very common default configuration for mobile email programs.

Each program using IMAP to access your email is simply keeping itself in sync with the master copy. So if something happens to the master copy — say an email is deleted or marked as “read” — then that change will be reflected in all the email programs.

Delete a message here, it’s deleted there. Mark it read there, it’ll show up as read here. IMAP enables cross-device synchronization.

IMAP: folders

Unlike POP3, IMAP supports folders.

If you create a folder on one machine connected to your email account using IMAP, then that folder becomes visible in all email programs connected to that email account via IMAP. And, of course, if you move a message into a folder, that message is moved into the folder in all email programs connected to that account.

The only common point of confusion is Gmail. Gmail doesn’t support folders at all, but instead provides roughly equivalent functionality through the use of labels. Check out my article How Do Gmail Labels Relate to Folders? for more.

IMAP: easy migration

This is an under-appreciated feature of IMAP.

If you place a message in your inbox on a machine that is connected to your email account via IMAP, that message is uploaded and placed in the master copy on the server.

In fact, that’s true for any folder, but the inbox has special significance, I think.

Why?

It’s what most people want to move when they’re changing email providers.

Moving from Yahoo! to Gmail? Set up a PC-based email program with an IMAP connection to each, and simply drag and drop the contents of the old inbox to the new.

Conceptually, it really is nearly that simple.

IMAP: backup

Let’s say you access Gmail via the web and only via the web. You have everything you need on any computer by logging into your Gmail account.

What about backup?

A machine running a desktop email program connected to your email account via IMAP makes for a great solution.

In fact, that’s exactly what I recommend these days. Most of your email access may be via your email provider’s web interface, but a machine running an email client like Thunderbird, connected to your accounts via IMAP, will download email as it appears.

As a backup.

IMAP: best when fast and connected; POP3: best for slow or intermittent

The POP3 email protocol was developed in the days of dial-up modems and temporary connections.

Connecting to the internet, downloading all your email, and disconnecting was a common way of life, particularly when no one could use the telephone while you were connected.

IMAP leverages a faster and more continuous connection to the internet. It’s more or less constantly checking for updates and synchronizing between your PC and the master email repository.

Both work in either scenario. POP3 works just fine if you’re always connected with a fast connection, and IMAP works if connectivity is not always present and synchronization actions need to be deferred until it is.

But if you are always connected and you are on something faster than a dial-up modem, IMAP might well make for a convenient approach to managing your desktop email.