Difference between POP3 and IMAP

POP3:

To get an e-mail for a customer from the ISP machine, there must be some protocol that contacts the message transfer agent (ISP machine) and it allows e-mail to be copied. This type of protocol is called Post Office Protocol Version 3 (POP3).

POP3 comes into play when the user starts a mail reader. The mail reader calls up the ISP to establish a TCP connection at port 110. It then follows three steps:

1. Authorisation: It deals with user log in.
2. Transaction: It deals with collecting the e-mail and marking them for deletion.
3. Updates: It deals with the deletion of marked e-mails.

IMAP:

IMAP allows messages to remain in the mailbox of the server indefinitely. It provides mechanisms for creating, manipulating and destroying mailboxes in the server.

The IMAP server listens to port number 143. Not every ISP or e-mail program supports both POP3 and IMAP protocols.

POP3 vs IMAP:

ParameterPOP3IMAP
Protocol Defined in1. RFC 19391. RFC 2060
TCP Port2. 1102. 143
E-mail stored in3. Local PC3. Central Server
E-mail read4. Offline4. Online
Connect time required5. Less5. More
Use of server6. Very less6. Extensive
Multiple mailboxes7. No7. Yes
Back up of mailbox done by8. User8. ISP