E-mail messages are sent to a mail server where the messages are stored on receipt in the e-mail box of the receiver. The messages in the mailbox of the recipient are received by the recipient using retrieval protocols. Some clients and servers prefer to use typically proprietary protocols that are specific to vendors, most others support the Internet standard protocols (SMTP) for sending e-mail and Internet Message Access Protocol (IMAP) for retrieving e-mails, allowing inter-operability with other servers and clients. Email client can generally be configured to use IMAP4 to retrieve e-mails and SMTP for sending the e-mails. The various e-mail protocols are:
- IMAP: It is an application layer Internet protocol that lets the local client to access E-mail on remote server. IMAP is frequently used in large networks to retrieve mails from the e-mail server. It is used in college-campuses in their mail system. this protocol also allows users the ability to access new messages immediately on their computer, since the mail is stored on the e-mail server.
- IMAP4: IMAP4 is naively capable of supporting encrypted login mechanism which makes it different from other Internet protocol. IMAP4 also transmit passwords as plain text. Some combinations of client and servers use plain-text passwords as the server and client must agree upon the encryption mechanism to be used. IMAP4 uses network port 143 to over a TCP/IP connection.
- Simple Mail Transfer protocol (SMTP): Referred to as SMTP, it is a protocol that facilitates transmission of e-mail messages between servers. A majority of e-mail system sending mails over the Internet employ SMTP to sand massages from server to server. The messages can then be retrieved with an e-mail client using either POP or IMAP. For messages top be sent from a mail client to a mail server, SMTP is used. therefore, it is Important to specify — the IMAP server, POP3 and the SMTP server, when an e-mail application is configured.