IMAP stands for Internet Message Access Protocol. When you read your Email, you do so via a computer program which is a mail client. Examples of mail clients include Outlook, Netscape Messanger, and Eudora. There are also Email clients for the Web, such as Hotmail, Yahoo Mail, and, especially, the Horde's Web Email client: IMP (see links at bottom of this page).

Your mail client reads mail by connecting to a mail server. That is what happens when you start your mail client and press the 'Get Mail' button (or whatever the button is called). Typically, your ISP (Internet Service Provider) runs the mail server to which your mail client connects to send and receive mail. IMAP has to do with receiving mail. IMAP is an alternative to POP (Post Office Protocol). When you first setup your Email client (Netscape, Outlook, or whatever), you enter the name or the IP (Internet Protocol) number of your mail server. Note, it is perfectly possible for you to connect to a mail server which is operated by someone other than your ISP.

So, as we were saying, your mail client is connects to your mail server and retrieves your mail. The difference between IMAP and POP is that IMAP leaves your mail on the server so that it is still there the next time you read mail. With POP, you download all your mail, delete mail you no longer are interested in, and store other mail in mail folders. With IMAP, it appears that you are doing exactly the same thing. However, with IMAP, the mail folders are on the server, not on your local client machine. This is good. It means that if you login to a different machine (say, your laptop instead of your desktop machine), then when you read your mail, you will see the same set of folders and not have to redownload all of your mail to that other machine. Also, with IMAP, you don't have to download large attachments. They can be left on the server and even deleted without you having to download them ever. With IMAP, your mail client just downloads the mail message headers (not the message bodies). You choose which message you wish to read, delete, search, or classify. All the action happens on the server. The only thing which gets downloaded by your client are just the messages that you actually read. Again, unlike POP, with IMAP, downloading does not mean removing from the server. Everything stays on the server.

I think is is now fair to say that the IMAP protocol is well implemented by many mail servers and many mail clients.

The coolest thing happening currently for IMAP that I know about is:

  http://www.horde.org/imp/about/

I started using IMAP instead of POP to recieve Email in mid 1998. Both the Netscape mail client (version 4.6) for Linux and the Netscape mail client (version 4.6) for Windows work very well as IMAP clients, connecting to my IMAP server running on Red Hat Linux 6.1.

Following is a very abbreviated history of my experience with IMAP.

After an initally favorable experiences using Netscape mail, loquaciously dubbed 'Netscape Messenger', version 4.05, I tried to switch to the new version 4.5. Disaster, as far as IMAP was concerned. What were a few tolerable glitches became un unusable comedy of bugs. At first I figured it might be my Imap server, since I am running a relatively old version of imapd on Linux. In my frustration, I went out and purchased Eudora Pro, as it claimed to support Imap. The result was pleasing. Eudora Pro worked fine with my existing Imap server on Linux, was able to detect and convert all of my Imap server-side folders without much intervention on my part, and, best of all, I have not seen the problems I had with Netscape 4.5 Imap mail.

However, Eudora Pro has several frustrating aspects. For example, it gives little control over which mail headers are viewable and trys its best to hide the precise email address of people, preferring to show you just the name in its address book entry for the person. It has other irritating quirks. I think Eudora must have been written by a programmer who knows how to program very well but isn't that great in designing user interfaces.

I also considered Pegasus Mail. But Pegasus mail did not support IMAP.

I stuck with Eudora for about a month, but then, after a rather easy upgrade to Red Hat Linux 5.2, which comes preequipped with Netscape 4.07, I was anxious to try Netscape on Linux. The result was good, except for the ugly fonts which X uses. I did a little research and, apparently, the X community is working on fixes to this ugly fonts issue. But there is a work around. Use Windows for the one thing it is good for: a network computer. Run an X server on Windows. I use X-Win32, which costs $200 and is worth every penny. I now display my UNIX applications which are running on Linux to X Windows within my Windows 95 box, via X-Win32, on a Phillips 19 inch high resolution monitor, running at 1280x1024 pixels.

The bottom line is: IMAP is ready for prime time, if used with the latest versions of the Netscape Email client.

To use IMAP, you must have an Email client which supports IMAP which connects to a mail server (normally, but not necessarily) at your ISP, which runs an IMAP server.

For a mail server, I happen to sysadmin my own mail server machine, Linux Red Hat 5.2, which runs an IMAP server, imapd. Configuration of imapd was trivial -- I just started it and it worked. Note, you can run both an IMAP and a POP server process on the same mail spool so that different users may choose whether they wish to use POP or IMAP clients (or both!).

IMAP links

horde.org
  Web-based clients of all kinds, including IMAP.

The IMAP Connection
   An extensive site at the University of Washington

IMAP vs. POP
   An old source document (c. 1993) by Terry Gray of the University of Washington

Non-Dairy Creamer Homepage
   Ian Smith's IMAP client Java middle-ware