What is IMAP?
Internet Message Access Protocol (IMAP) is a standard protocol for accessing email from your local computer. IMAP is a client/server protocol in which email is received and held for you on the servers. You (by using your email client, such as Outlook Express, Netscape Messenger or Eudora) can view just the header information, which includes the sender and subject of the letter, allowing you to decide whether to download the message or not. You can also create and manipulate folders or mailboxes on the server, delete messages, or search for certain parts or an entire note.
What is POP3?
Post Office Protocol 3 (POP3) is also a standard protocol for receiving email and is also a client/server protocol in which email is received and held for you on the servers. With POP3, your mail is saved in a mailbox on the remote server until you check your mail. When you check your mail, all of the mail is immediately downloaded to your computer and is no longer maintained on the server.
What's the Difference?
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 often one will suit your needs better than the other.
What are the Benefits of IMAP?
Since you can view just the header information without downloading the entire message, you can delete large messages without wasting time for downloading them. Also, because the messages remain on the server, you can access your mail from multiple locations and ensure that your messages are always available for you. And, with the messages remaining on the servers if your computer crashes you don't have to worry about losing your messages.
What are the Benefits of POP3?
Since all of your messages are downloaded immediately, after you check your mail at your computer, you do not need to actually 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 because the messages do not stay on the servers.
What are the Drawbacks to IMAP?
Unlike POP3, IMAP requires continual access to the server during the time that you are working with your mail. Also, because 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.
What are the Drawbacks to 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. Because POP3 downloads all the mail on the server at once, people are occasionally unable to successfully receive their messages because POP3 will get stuck or disconnect when trying to download large messages. To fix this people will either need to contact tech support or log onto our web mail system to delete the large messages themselves. 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.