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 e-mails 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:
| Parameter | POP3 | IMAP |
| Protocol Defined in | 1. RFC 1939 | 1. RFC 2060 |
| TCP Port | 2. 110 | 2. 143 |
| E-mail stored in | 3. Local PC | 3. Central Server |
| E-mail read | 4. Offline | 4. Online |
| Connect time required | 5. Less | 5. More |
| Use of server | 6. Very less | 6. Extensive |
| Multiple mailboxes | 7. No | 7. Yes |
| Back up of mailbox done by | 8. User | 8. ISP |