University of California, Riverside




POP and IMAP are two protocols that mail programs use to access mail from an email server.

How do I know if I normally use IMAP or POP to check my mail?

The vast majority of users access their mail using POP. However, you can check by going to your email client's Tools and checking what is selected.

What's the difference between IMAP and POP?

IMAP works by keeping mail on the server. POP works by downloading your mail to your computer.

What does this mean to me?

Using POP to check mail will give you access to new mail only when you check mail from the web while away from your main computer. Once you check your mail and it is downloaded from Eudora or Outlook it is removed from the email server.

Using IMAP to check your mail keeps all of your email and email folders on the server which can then be accessed via your email client or using the Webmail interface through your web browser.

"POP" stands for "Post Office Protocol"

A POP account downloads mail to your local computer by default. Often, when a message is downloaded, it is deleted from the mail server. This prevents you from reading the same messages when you go to a different computer. Some mail clients, including Eudora and Outlook, let you tell POP servers to "Leave Mail on Server" for a certain period of time. This allows you to read the same messages again from another computer, if necessary. You might want to do this if you read your mail from computers at work and at home, or on a desktop and a laptop computer.

The advantage of POP mail is that you have your messages with you and can peruse them even while you are not connected to the Internet.

The disadvantage is that it is difficult to keep multiple computers synchronized. Messages you send from one computer are not copied on the other computers.

"IMAP" stands for "Internet Message Access Protocol."

It is better than POP for accessing mail from multiple locations because it leaves the mail messages on the mail server. This lets you read the same messages regardless of what computer you use to read your e-mail. Messages you send are also stored on the mail server (if you keep copies, which is a good idea), so if you send a message from work, you will see that message when you access your mail from home or from a laptop while on the road. When you use an IMAP account you are, in fact, viewing your e-mail that is stored on UCR's email server. There are no copies of the messages stored on your local computer unless you make a special effort to copy them there.

Because with IMAP your messages are kept indefinitely, you must remember there is an upper limit on the amount of mail storage you can use on the server, it is 250MB. If you get a lot of mail your account can fill up so it is recommended that you closely monitor the space being used. One caveat is that to use IMAP requires the computer be connected to internet.

More Information 

General Campus Information

University of California, Riverside
900 University Ave.
Riverside, CA 92521
Tel: (951) 827-1012

Department Information

Computing & Communications
Computing & Communications Bldg.

Tel: (951) 827-4741
Fax: (951) 827-4541