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The Difference Between POP and IMAP Email Protocols

October 31, 2009DavidEmail0

The POP or POP3 and IMAP are the two of the major internet email protocols used today; therefore it’s worth taking a look at these different ways of getting to your email. As people ask, “What is the difference between email protocols?”.

The first thing to understand about email before talking about email protocols is that when someone sends you an email, this email eventually winds up at the mailserver of your ISP before it makes it to your inbox. Think of this mailserver as the traditional post office, receiving, sorting, and storing mail until it’s time for delivery. Once the email message has reached your ISP’s mailserver, the POP3 and IMAP protocols are the methods you use to acutally “pick-up” or receive the message. Generally all of this happens relatively quickly, (just try sending yourself an email), but now that we have a little bit of structural understanding of when the protocols are used, we can talk about each one.

The POP or POP3 email protocol is most useful when you are using one computer to manage your email. The POP protocol will contact the mailserver, and download the messages to your local computer. Once you have downloaded the emails from the mailserver, they are no longer available on the mailserver (with an exception which we will go over shortly). This is advantageous because all of your email is stored and available locally and instantly on your computer, whether you are online or not online. But because you are downloading the messages from the server to your local machine, once you’ve downloaded the messages, they will not be available on the mailserver for you to view from other computers.

Consider the example of the traditional post office. If you tell a friend to pick up a package for you, but forget that you told your friend to pick it up for you, and picked it up yourself, there will be no package there when you friend gets to the post office. Accordingly, if your computer is automatically set to check and download emails every 15 minutes (which many machines running Outlook are configured to do), if you went on the road and checked your email account via webmail, you may not see all of your messages because some may have been already downloaded by the mail client (E.g. Outlook) running on your local machine.

To avoid this problem, Outlook has a feature that enables you to leave a copy of the mail on the server for a specified number of days, and to only delete the email from the server once you’ve delted it locally. This is a very handy feature, but with the disadvantage that sometimes multiple copies of emails begin to float around.

Enter IMAP. In the IMAP email model, all of the messages are always stored on the server and are never downloaded locally. Thus, IMAP gives you incredible flexiblity. No matter where you check your email, or from which computer, you will always see the exact contents of your email the same way. I work on two different laptops and a desktop machine, and it’s critical to me that I see all of my email the same way on all machines (unlike the POP example where I may “miss” an email if it’s already been downloaded). Naturally you need to have a reliable ISP as well as ample storage space on your server. That being said, it’s smart to download any very large attachments and then delete the message from the server to free up mailbox storage space.

In contrast to POP, you must be online to be able to view your messages if you are using the IMAP protocol, as IMAP requires you to be online as all of the messages are stored on the server.

A final consideration about the POP vs IMAP protocol is the ability to backup your messages.  Using the POP protocol and a program like Outlook, it’s very easy to backup your messages (usually into an outlook .PST file which you can later restore).  Because IMAP doesn’t download the messages, the above method won’t work.  Fortunately there are some very good programs out there that can connect to your IMAP mailserver and create copies of the emails that are there.  One such program is the freeware, IMAPSize, which I review in this post.

So in the end it all comes down to personal choice. Many people are now using free webmail-based services such as Gmail, Yahoo! Mail, and Hotmail to handle their email needs, and since most people access these accounts via a web browser, the POP/IMAP protocol debate doesn’t apply (though with some of these services you can use POP and IMAP to interact with a local email client).   For most home users, who will mostly access their email on a single computer, and have occasional ISP-webmail use (e.g Comcast or Time Warner webmail), the POP protocol is quite adequate.   As long as you remember to have your email client leave a copy of the messages on the server so you don’t miss any emails that your computer downloaed before you checked via webmail, you should be fine.

But for the more on the go or business user, who lacks the infrastrucure of an exchange server  or uses multiple computers, IMAP is great way to go.  Personally, I switched about 4 years ago, and haven’t looked back since!

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