Email: IMAP vs. POP FAQ

Article ID: 310

What is IMAP?

Internet Message Access Protocol (IMAP) is an Internet protocol that allows a client to manipulate electronic mail messages that are stored on a mail server. It allows clients to manipulate a remote message folder (called a mailbox) in the same way they would manipulate local mailboxes. It supports mail operations that let users create, delete, and rename mailboxes; check for new messages; permanently remove messages; set and clear flags; and search.

Post Office Protocol (POP) is an Internet mail server protocol that provides an incoming message storage system. It works in conjunction with the SMTP (Simple Mail Transfer Protocol), which provides the message transport services required to move mail from one system to another. The current version is called POP3.

IMAP can be thought of as a remote file server, while POP3 can be thought of as a "store-and-forward" service. Ultimately, they both accomplish similar tasks, but POP was kept more simple by design, whereas IMAP is more complex. You use one or the other depending on what you need/want.

Since you can view just the header information without downloading the entire message, you can delete large messages you do not need without wasting time downloading them. There are benefits to leaving the messages on the server. You can access your mail from multiple locations and ensure that your messages are always available for you, and, if your computer crashes, you do not have to worry about losing your messages.

Since all of your messages are downloaded immediately when checking mail at your computer, you do not need to be connected to the Internet to read your email. Also, because the messages are downloaded to your computer, you do not need to worry about accruing disk usage charges from having large amounts of email on the server.

Unlike POP3, IMAP requires continual access to the server during the time that you are working with your mail. Since the messages are stored on the server, it becomes much easier to go over your disk quota. However, you can reduce this risk by taking specific steps to not leave your Sent Mail, Drafts or Trash on the server. And like any new service, there is a slight learning curve to get used to IMAP since most people are used to using POP3.

The major drawback to POP3 is that it is an older protocol that was designed before people were able to easily send large emails with attachments. POP3 downloads all of the mail on the server at once, therefore people are occasionally unable to successfully receive their messages. This is because POP3 will get stuck or disconnect while trying to download large messages. To fix this you will need to contact Customer Support. Also, if you use POP3 and are traveling or check your mail from multiple locations, you will not be able to view any of your old mail because the messages only exist on the computer on which you originally received your mail.

POP3 is not compatible with our WebMail program. If you use WebMail we highly recommend that you change the settings in your email client to use IMAP in order to prevent any conflicts.

• When downloading from POP3 and IMAP at the same time, occasionally the POP3 client will download half of a message before it is interrupted by the IMAP session and leave a fragmented message behind.
• Sometimes while reading mail in IMAP, the messages will not be downloaded by a POP3 session as it thinks they have already been read.
• Folders created with IMAP will not show up with an email client configured using POP3.
• POP3 will remove messages from the server when downloaded by default (unless a setting is changed), so the messages will no longer be viewable in IMAP.
• IMAP deletes the messages permanently when you remove them by default (unless a setting is changed), where POP3 will save them in a trash folder in the POP3 configured email client.

Last modified 4/29/2005

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