hi stainzz Email servers are probably about the most complicated servers to set up because not only is there a huge number of security implications to running your own mail server but they also tend to be split up into many small parts taht all do different, highly specialized, things. This page aims to give you an overview of how and email system works. I don't pretend to be an expert on these things but this should be a good starting point.

At the pointy end of the system is the MTA which stands for mail transport agent. This is the bit that does the grunt work of moving email around on the Internet. Probably the most popular MTA is sendmail but there are plenty of others to choose from including courier-mta, postfix and qmail as well as pay for offerings. The MTA probably has the most security issues as it is world facing. There used to be problems (and to some extent there still is) with open relays. These are badly configured MTAs that allow anyone to connect and send email through them. Many modern MTAs make it deliberately quite difficult to configure an open realy.

The next step down is the MDA or mail delivery agent. This has the job of deliverying the email to the user. Typically this means placing the email in a mbox or maildir. A popular MDA is maildrop but, as with MTAs, plenty of other exist (for instance procmail). As well as deliverying the mail the MDA often filters the mail as well. This can be just a simple set of rules for putting certain email in certain folders or it can be as complex as intergrating multiple external mail scanners that check to spam and viruses.

Depending on the set up the next part of the puzzle is optional but almost always present and is either an IMAP or POP server. If you are setting up your own system I strongly recommend an IMAP server as it means that you will be able to easily check your mail from anywhere in the world. Again there are loads of IMAP servers but they vary in quality. I use the Courier IMAP server and have found it to be quite reliable if a little slow. The IMAP server essentailly owns your mailbox (I use mailbox here not to refere to the mbox file format but a generic place that holds you mail) and provides a view of it to the next layer of software, the MUA.

The MUA is the bottom rung of the ladder and stands for mail user agent. This is the application that you actually read you email with. The reason that the layer above is optional is because there are a few MUAs that can directly read mbox format files (there might be some that can read maildirs as well). These are rare though and I wouldn't recommend using them. It is much better to get a decent MUA (such as Thunderbird, KMail, Evolution, etc, etc) that can interface with and IMAP server

this is taken from source http://www.crazysquirrel.com/comput ing/debian/mail.jspx

Answered by laks , an ibibo Master, at 3:39 PM on May 27, 2008

E-mail (electronic mail) is the exchange of computer-stored messages by telecommunication. E-mail messages are usually encoded in ASCII text. However, you can also send non-text files, such as graphic images and sound files, as attachments sent in binary streams.E-mail is one of the protocols included with the Transport Control Protocol/Internet Protocol (TCP/IP) suite of protocols. A popular protocol for sending e-mail is Simple Mail Transfer Protocol.
It works while you compose your message, you send it. These message is in a little digital packate of information that is sent through a cable from your computer to another computer maintained by your e-mail service provider, which is called a mail server. The mail server examines the recipient's address to decide how to route the message.
What is e-mail? In its simplest form, e-mail is an electronic message sent from one device to another. While most messages go from computer to computer, e-mail can also be sent and received by mobile phones, PDAs and other portable devices. With e-mail, you can send and receive personal and business-related messages with attachments, such as photos or formatted documents. You can also send music, video clips and software programs.

Answered by Om Prakash , an ibibo Master, at 7:27 PM on May 13, 2008

Every day, the citizens of the Internet send each other billions of e-mail messages. If you're online a lot, you yourself may send a dozen or more e-mails each day without even thinking about it. Obviously, e-mail has become an extremely popular communication tool.

Have you ever wondered how e-mail gets from your computer to a friend halfway around the world? What is a POP3 server, and how does it hold your mail? The answers may surprise you, because it turns out that e-mail is an incredibly simple system at its core. In this article, we'll take an in-depth look at e-mail and how it works.
It work is :-
It can take days to send a letter across the country and weeks to go around the world. To save time and money, more and more people are relying on electronic mail. It's fast, easy and much cheaper than the using the postal service.

What is e-mail? In its simplest form, e-mail is an electronic message sent from one device to another. While most messages go from computer to computer, e-mail can also be sent and received by mobile phones, PDAs and other portable devices. With e-mail, you can send and receive personal and business-related messages with attachments, such as photos or formatted documents. You can also send music, video clips and software programs.

Answered by Sharad Singh , an ibibo Master, at 6:17 PM on May 12, 2008

well stainzz,Every day, the citizens of the Internet send each other billions of e-mail messages. If you're online a lot, you yourself may send a dozen or more e-mails each day without even thinking about it. Obviously, e-mail has become an extremely popular communication tool.

Have you ever wondered how e-mail gets from your computer to a friend halfway around the world? What is a POP3 server, and how does it hold your mail? The answers may surprise you, because it turns out that e-mail is an incredibly simple system at its core. In this article, we'll take an in-depth look at e-mail and how it works.
It work is :-
It can take days to send a letter across the country and weeks to go around the world. To save time and money, more and more people are relying on electronic mail. It's fast, easy and much cheaper than the using the postal service.

What is e-mail? In its simplest form, e-mail is an electronic message sent from one device to another. While most messages go from computer to computer, e-mail can also be sent and received by mobile phones, PDAs and other portable devices. With e-mail, you can send and receive personal and business-related messages with attachments, such as photos or formatted documents. You can also send music, video clips and software programs.

Answered by satyaiitk , an ibibo Master, at 5:06 PM on May 08, 2008

E-mail (electronic mail) is the exchange of computer-stored messages by telecommunication. E-mail messages are usually encoded in ASCII text. However, you can also send non-text files, such as graphic images and sound files, as attachments sent in binary streams.E-mail is one of the protocols included with the Transport Control Protocol/Internet Protocol (TCP/IP) suite of protocols. A popular protocol for sending e-mail is Simple Mail Transfer Protocol.
It works while you compose your message, you send it. These message is in a little digital packate of information that is sent through a cable from your computer to another computer maintained by your e-mail service provider, which is called a mail server. The mail server examines the recipient's address to decide how to route the message.
The message travels over the Internet, reach at the mail server of the recipient's e-mail service provider, where it is held in an electronic mailbox. When the recipient checks for new messages, their e-mail client communicates with their e-mail service provider's mail server and retrieves any new messages waiting in that electronic mailbox.

Answered by shaista , an ibibo Master, at 2:52 PM on May 08, 2008

Let us dissect an e-mail address and see how it works
In jennyb@mtu.edu, for example, everything to the right of the @ symbol relates to the actual computer where the mailbox account is held, while everything to the left of the @ symbol relates to the user at that address.
This means that the name of the computer where a user called Jenny Borg has a mailbox (can also be called userid or account and is similar to a login on a LAN), is mtu.edu.
An email address works on the same principle as a telephone number. A telephone number in a suburb of Princeton, U.S.A. is 001-609-951 9638.

Answered by Nishu's , an ibibo Master, at 7:09 PM on May 07, 2008

Using an e-mail program, or client, you compose your message. Then you send it. These message is a little digital package of information that is sent through a cable from your computer to another computer maintained by your e-mail service provider, which is called a mail server. The mail server examines the recipient's address to decide how to route the message.

The message then travels over the Internet, arriving at the mail server of the recipient's e-mail service provider, where it is held in an electronic mailbox. When the recipient checks for new messages, their e-mail client communicates with their e-mail service provider's mail server and retrieves any new messages waiting in that electronic mailbox.

Answered by Ashish Yadav , an ibibo Wizard, at 5:53 PM on May 07, 2008

E-mail (electronic mail) is the exchange of computer-stored messages by telecommunication.E-mail messages are usually encoded in ASCII text. However, you can also send non-text files, such as graphic images and sound files, as attachments sent in binary streams.E-mail is one of the protocols included with the Transport Control Protocol/Internet Protocol (TCP/IP) suite of protocols. A popular protocol for sending e-mail is Simple Mail Transfer Protocol.

Answered by Kajal Sharma , an ibibo Master, at 4:44 PM on May 07, 2008

well,E-mail, short for electronic mail and often abbreviated to e-mail, email or simply mail, is a store and forward method of composing, sending, receiving and storing messages over electronic communication systems. The term "e-mail" (as a noun or verb) applies both to the Internet e-mail system based on the Simple Mail Transfer Protocol (SMTP) and to X.400 systems, and to intranet systems allowing users within one organization to e-mail each other. Intranets may use the Internet protocols or X.400 protocols for internal e-mail service supporting workgroup collaboration. E-mail is often used to deliver bulk unsolicited messages, or "spam", but filter programs exist which can automatically delete some or most of these, depending on the situation.

Just as a letter makes stops at different postal stations along the way to its final destination, e-mail passes from one computer, known as a mail server, to another as it travels over the Internet. Once it arrives at the destination mail server, it's stored in an electronic mailbox until the recipient retrieves it. This whole process can take seconds, allowing you to quickly communicate with people around the world at any time of the day or night.
To receive e-mail, you need an account on a mail server. This is similar to having a postal box where you receive letters. One advantage over regular mail is that you can retrieve your e-mail from any location on earth, provide that you have Internet access. Once you connect to your mail server, you download your messages to your computer or wireless device, or read them online.

Source site:

1) http://en.wikipedia.org/wiki/E -mail
2) http://www.learnthenet.com/eng lish/html/20how.htm

Answered by Saurabh , an ibibo Master, at 2:07 PM on May 07, 2008

stainzz Email provides a fast, efficient delivery system for text-based messages. As with all applications on the Internet, it uses certain protocols to achieve this,as SMTP (Simple Mail Transfer Protocol) is used to distribute mail between servers, and by the mail client to send the message initially;

POP (Post Office Protocol) is used by the mail client to download messages and headers to a local computer from the mail server. POP is useful if you want to read your mail offline (ie not connected to your mailserver), as it downloads and stores your email on your own computer.

IMAP (Internet Message Access Protocol) is used by clients to access mail directly on the mail server. With IMAP, the mail usually stays stored on the recipient's server until it is deleted - the mail client only views the mail, rather than downloading it.

On campus, it's possible to use either IMAP or POP; if you access your mail with the Mulberry, Simeon or Execmail clients, then you're probably using IMAP, whereas if you use Eudora, Outlook or Netscape to access mail, then you're most likely using POP.
for more inf check source http://services.ex.ac.uk/cmit/modul es/the_internet/slides/sec-howemail works.html
or else check
How does email travel when I receive or send an email message?
When Lisa sends Bob an email message (Figure B), the following is a simplified step-by-step of how it travels:

1. Lisa opens her email program (Outlook Express), uses her email account, lisa@otherisp.com, and writes an email message to bob@comentum.com. Her Outlook Express sends the message through TCP port 25 of Lisa’s Internet connection, then to the other ISP’s SMTP server (still on TCP port 25).

2. The other ISP’s SMTP server finds the destination’s SMTP server (in this case, Comentum) and sends the message out to Comentum’s SMTP server (through TCP port 25 of her Internet connection).

3. Comentum’s SMTP server sends the message to Comentum’s POP3 server where the message waits for Bob to pick it up.

4. Bob opens his email program (Outlook Express) and when he clicks Send/Recv button, his Outlook Express sends a request through Bob’s Internet connection to Comentum’s Pop3 server (through TCP port 110) and downloads Bob’s message to Bob’s computer where he sees Lisa’s message.

The same process happens in reverse, when Bob sends Lisa an email message (Figure A on the front).
* There are other network elements that are necessary to make this process happen, such as: Comentum’s routers, Comentum’s DNS servers and Comentum’s Internet connection, and other ISP’s routers, DNS servers and Internet connection. We left those elements out and concentrated on email clients and email servers.
** Bob may use a different ISP for his Internet connection and to host his domain, website and email (bob@hiscompany.com.) Bob@hiscompany.com uses the same Comentum mail servers
for more inf check source http://www.comentum.com/how-email-w orks.html

Answered by raj u , an ibibo Master, at 1:43 PM on May 07, 2008