Frequently asked quesitions about IMAP

 

What are the differences between IMAP and POP?

Both IMAP (Internet Message Access Protocol) and POP (Post Office Protocol) are ways to access email messages that are stored on a mail server such as the Calmail server on the Berkeley campus. IMAP can do everything that POP can do and more. However, it does some functions differently from POP, and these differences have an impact on how you use your email software (such Thunderbird).

With POP, all messages are stored in a single location on the server. When your email program retrieves messages using POP, all messages are downloaded to your computer. Depending on how your software is configured, the messages may be automatically removed from the server when your retrieve them or they may be left on the server. If you have multiple mailboxes and your mail software is using POP, those mailboxes exist just on your computer. That is why if you retrieve your messages from multiple locations, the mailboxes you have on the different computers will not be the same.

Although POP and IMAP can do many of the same things, POP is geared towards having the primary location of messages be on the user's computer, whereas IMAP in contrast is geared towards having the server be the primary location of messages. With IMAP, you can have multiple mailboxes on the email server, and these same mailboxes will appear everywhere you retrieve your mail.

If you are interested in the differences between IMAP and POP from a technical perspective, please see Comparing Two Approaches to Remote Mailbox Access: IMAP vs. POP.

How do I benefit from IMAP? What are the advantages compared to POP?

IMAP has a number of advantages over POP. For users who need to retrieve messages from multiple locations, IMAP is far more convenient. With POP, there is no easy way to have all your incoming and outgoing messages be in the same places on all your computers. If you want copies of all the messages you sent on both your home and work computers, for instance, you have to send a copy of each message to yourself and then move the message to the Out box on the computer that did not send the message.

In addition, because of IMAP's server-orientation, you do not have to clutter up your computer with files you don't need. Attachments by default will not be saved on your computer unless you choose to download them. Also, unless you choose to download all messages, you will notice better performance with IMAP since only the message headers (sender, subject, date, etc., but not the body of the message, embedded photos, and so forth) are downloaded from the server until you actually open the message.

Unlike POP, IMAP is a protocol that continues to be enhanced. For example, IMAP has a feature that allows server mailboxes to be searched; no such feature is available in POP.

I only check mail from one computer and at work only. How would I benefit from IMAP?

In addition to the benefits listed above, another advantage of IMAP is that mail stored on a server such Calmail is regularly backed up.

Also, if your computer ever breaks down, you can easily check your mail from another computer.

If the server is down, how do I see my stored messages?

Once you have viewed a message, it is stored ("cached") on your computer, so you will be able to read that message again, even if the server is down.

You can choose to have your email software download all messages using IMAP, just like with POP, so that all messages previously retrieved can be read even if the server is down; configuring your email software to work in this way can be a good idea for people who have portable computers and often go into areas where a network is not available.

I worry about privacy. Is my email less private in IMAP?

No. Email privacy is greater with IMAP because by default all messages are not automatically downloaded to your computer. You can also easily remove any messages you want from the server. You can choose to delete the messages or move them to a "local mailbox" that exists only on your computer.