IMAP and POP are the two different approaches to build a distributed electronic mail infrastructure. Pop is the oldest method and best known. But, IMAP provides good support for the three modes of remote mailbox access such as offline, online and disconnected.
POP (Post Office Protocol)
It was mainly designed to provide support to ‘offline’ mail processing. Pop downloads all the messages from the server to user’s own machine in one pop. All the downloaded mails are then processed in client machine. Once the messages are downloaded they are deleted from the mail server. Since the original messages are deleted from the server, the messages are tied to a single machine and cannot be accessed by webmail or any other client. Pop is limited to a single user.
Disadvantages of POP
1. Downloading mails will take time.
2. There is only one mailbox exist in server.
3. Mails can be transfered only to local mailboxes.
4. Outgoing emails can be stored only in the local desktop PC.
IMAP (Internet Message Access Protocol)
IMAP can also perform offline mail processings but, it is more efficient to use it in online and disconnected operation. In IMAP mails can be accessed from many email clients or webmail interfaces because the mails are saved in the server until the user deletes them. It has a richer functionality to manipulate ones inbox. IMAP can manipulate the message status flags such as ’seen’, ‘deleted’, ‘answered’ and some user defined flags. IMAP is the best option for people who want to access their mails from many locations.
Disadvantages of IMAP
1. IMAP is a complex protocol.
2. Mails are not available when offline.