1. Protocols:
Basically, a protocol is about a standard method used at each end of a communication channel, in order to properly transmit information. In order to deal with your email you must use a mail client to access a mail server. The mail client and mail server can exchange information with each other using a variety of protocols.
1.1. For Email Retrieving
Ø IMAP Protocol:
IMAP (Internet Message Access Protocol) – Is a standard protocol for accessing e-mail from your local server. IMAP is a client/server protocol in which e-mail is received and held for you by your Internet server. As this requires only a small data transfer this works well even over a slow connection such as a modem. Only if you request to read a specific email message will it be downloaded from the server. You can also create and manipulate folders or mailboxes on the server, delete messages etc.
Ø POP3 Protocol:
The POP (Post Office Protocol 3) protocol provides a simple, standardized way for users to access mailboxes and download messages to their computers.
When using the POP protocol all your email messages will be downloaded from the mail server to your local computer. You can choose to leave copies of your emails on the server as well. The advantage is that once your messages are downloaded you can cut the internet connection and read your email at your leisure without incurring further communication costs. On the other hand you might have transferred a lot of message (including spam or viruses) in which you are not at all interested at this point.
1.2. For Email Sending
Ø SMTP Protocol:
The SMTP (Simple Mail Transfer Protocol) protocol is used by the Mail Transfer Agent (MTA) to deliver your email to the recipient's mail server. The SMTP protocol can only be used to send emails, not to receive them. Depending on your network / ISP settings, you may only be able to use the SMTP protocol under certain conditions.
Ø HTTP Protocol:
The HTTP protocol is not a protocol dedicated for email communications, but it can be used for accessing your mailbox. Also called web based email, this protocol can be used to compose or retrieve emails from and your account. Hotmail is a good example of using HTTP as an email protocol.
Ø MAPI (Messaging Application Program Interface) definition
2. IMAP
IMAP stands for Internet Mail Access Protocol. There exist five versions of IMAP as follows:
1. Original IMAP
2. IMAP2
3. IMAP3
4. IMAP2bis
5. IMAP4
Key Points:
· IMAP allows the client program to manipulate the e-mail message on the server without downloading them on the local computer.
· The e-mail is hold and maintained by the remote server.
· It enables us to take any action such as downloading, delete the mail without reading the mail. It enables us to create, manipulate and delete remote message folders called mail boxes.
· IMAP enables the users to search the e-mails.
· It allows concurrent access to multiple mailboxes on multiple mail servers.
· By default, the IMAP protocol works on two ports:
o Port 143 - this is the default IMAP non-encrypted port
o Port 993 - this is the port you need to use if you want to connect using IMAP securely
3. POP3
POP stands for Post Office Protocol Version3.
Key Points
· POP3 is an application layer internet standard protocol.
· Since POP3 supports offline access to the messages, thus requires less internet usage time.
· POP3 does not allow search facility.
· In order to access the messaged, it is necessary to download them.
· It allows only one mailbox to be created on server.
· It is not suitable for accessing non mail data.
· POP commands are generally abbreviated into codes of three or four letters.
· By default, the POP3 protocol works on two ports:
o Port 110 - this is the default POP3 non-encrypted port
o Port 995 - this is the port you need to use if you want to connect using POP3 securely
4. SMTP
SMTP stands for Simple Mail Transfer Protocol. It is a standard protocol used for sending e-mail efficiently and reliably over the internet.
Key Points:
· SMTP is application level protocol.
· SMTP is connection oriented protocol.
· SMTP is text based protocol.
· It handles exchange of messages between e-mail servers over TCP/IP network.
· Apart from transferring e-mail, SMPT also provides notification regarding incoming mail.
· When you send e-mail, your e-mail client sends it to your e-mail server which further contacts the recipient mail server using SMTP client.
· These SMTP commands specify the sender’s and receiver’s e-mail address, along with the message to be send.
· The exchange of commands between servers is carried out without intervention of any user.
· In case, message cannot be delivered, an error report is sent to the sender which makes SMTP a reliable protocol.
· By default, the SMTP protocol works on three ports:
o Port 25 - this is the default SMTP non-encrypted port
o Port 2525 - this port is opened on all Site Ground servers in case port 25 is filtered (by your ISP for example) and you want to send non-encrypted emails with SMTP
o Port 465 - this is the port used, if you want to send messages using SMTP securely
5. MAPI (Messaging Application Program Interface)
MAPI (Messaging Application Program Interface) is a Microsoft Windows program interface that enables you to send e-mail from within a Windows application and attach the document you are working on to the e-mail note. Applications that take advantage of MAPI include word processors, spreadsheets, and graphics applications. MAPI-compatible applications typically include a Send Mail or Send in the File pull-down menu of the application. Selecting one of these sends a request to a MAPI server. MAPI consists of a standard set of C language functions that are stored in a program library known as a dynamic link library (DLL). Developers who are using Microsoft's Active Server Page (ASP) technology access the MAPI library by using Microsoft's Collaboration Data Objects (CDO). The CDO library comes with Microsoft's Internet Information Server (IIS). MAPI functions can be accessed by Visual Basic developers through a Basic-to-C translation layer.
Eudora, one of the most popular e-mail programs, includes a MAPI server. To activate the Eudora MAPI server, select Options from the Tools pull-down menu and then double-click on MAPI and specify whether MAPI should always be active or whether it should be active only when Eudora is running. Microsoft Exchange and possibly some other programs may require that you turn the MAPI server off when they are in use.
6. HTTP protocol
The HTTP protocol is not a protocol dedicated for email communications, but it can be used for accessing your mailbox. Also called web based email, this protocol can be used to compose or retrieve emails from and your account. Hotmail is a good example of using HTTP as an email protocol.