What is Internet email?
Internet electronic mail (email) refers to the use of the Internet to send and receive electronic messages or email. These messages can be plain text or non-text or a combination of both.

How does Internet email work?
The mechanism whereby an email is composed, sent and delivered over the Internet is discussed below.
Composing the Email
The user composes his email message using the user agent (UA - Example : Outlook Express) which provides the user interface to compose and send the email. Typically this will be an email program running on the user's computer e.g. Pegasus Mail, Eudora, Netscape Messenger, Outlook Express, Lotus Notes, GroupWise, etc. The email program will normally have at the least basic text editing capabilities so that the user can compose and edit his email efficiently. After composing the message, the UA will send it.
The Mail (SMTP) Server
The UA contacts the mail server. This mail server can be on the same computer as the UA itself or it can be on a network which can be reached by the user's computer. Note that in many cases it is on the Internet itself as in the case of a dial-up Internet user. The UA communicates with the mail server using a protocol known as Simple Mail Transfer Protocol (SMTP). It consists of a series of textual commands and replies. After establishing that the mail server is willing to accept the mail, the UA will transmit the sender and receipient email addresses and then the email message. The SMTP server after receving the full email from the UA will store it temporarily in its mail queue. This queue will be processed at regular intervals which can vary considerably from system to system.
Relaying the Email
The queued mail on the SMTP server is sent on using a Message Transfer Agent or MTA. The MTA transfers mail between two systems using the SMTP protocol. The MTA will also need to resolve the receipient's email address domain using the Domain Name Service (DNS) so that it can know how to route the mail. The mail may go through several relay MTA systems before it can get to its destination. At each MTA system the mail may be queued before it is relayed on. Ultimately the mail is transferred to its destination computer system where it is stored in the receipient's mailbox for retrieval.
Retrieving the EMail
Internet email is usually delivered to a mailbox residing on a computer system which has an MTA running on it to receive email. The nature of the SMTP protocol is such that the destination MTA is usually assumed to be available online, i.e. the computer system has a permanent link to the Internet. This is not a problem with organisations that have a leased line link to the Internet but it is a problem with dialup links and home uers. To overcome this, a node which can support an MTA can offer a maildrop service to the sites which do not have a permanent connection. The email is received on the maildrop node and stored there in the receipient's mailbox. The receipient can then contact the maildrop host at his convenience to retrieve the email. Password is the most common form of user authentication. The POP3 and IMAP4 protocols offer such a service. Currently POP3 is very widely used all over the Internet but IMAP4 should become more popular in due course since it has more and better features. Under POP3, the user will logon to the POP3 server which contains the user's mailbox and after successful authentication, the user will download his email messages. He has a choice of whether to delete off these messages from the POP3 server after download. Apart from this feature, there is very little else that he can do on the server. He cannot for example read the email off the server without downloading it or place it in a different folder on the server. POP3 is useful as an offline mail access system and it is simple, stable and very widely used. IMAP4 is designed to overcome many of the problems plaguing POP3, especially for online and disconnected email access.
What's the difference between POP and IMAP?
The brief explanation below is taken from Terry Gray's "imap.vs.pop" document in the IMAP distribution. The full document can be found in ftp://ftp.cac.washington.edu/mail/imap.vs.pop With POP (Post Office Protocol), mail is delivered to a shared server, and a personal computer user periodically connects to the server and downloads all of the pending mail to the "client" machine. Thereafter, all mail processing is local to the client machine. Think of POP as providing a store-and-forward service, intended to move mail (on demand) from an intermediate server (drop point) to a single destination machine, usually a PC or Mac. Once delivered to the PC or Mac, the messages are typically deleted from the POP server. IMAP is a client-server mail protocol designed to permit manipulation of remote mailboxes as if they were local. With IMAP, mail is again delivered to a shared server, but the mail client machine does not normally copy it all at once and then delete it from the server. It's more of a client-server model, where the IMAP client can ask the server for headers, or the bodies of specified messages, or to search for messages meeting certain criteria. Messages in the mail repository can be marked as deleted and subsequently expunged, but they stay on the repository until the user takes such action.
Reading the Email
No matter which protocol the user uses, at the end he will use his UA again to retireve the email and read its contents. Again this will typically be done on the user's PC or workstation.

What do I need to be able to use Internet email?
Basically you will need the following: Some form of Internet access
Access to a computer system
Software for the following functions:
composing the mail message,
sending and receiving email messages,
reading the mail message,
managing the mail messages
Typically all of the above functionalities are incorporated in the email software package that a user uses.


What are the software available for my PC?
Some popular email software for PC users which support POP3 include: Win95/98/NT: Pegasus Mail, Netscape Communicator, Eudora, MSOutlook Express, Pine, WinMail, Agent Windows 3.x: Netscape Communicator, Eudora, Pegasus Mail, WinMail, Agent MSDOS: Pegasus Mail, NuPOP, Minuet, Arachne Unix/Linux: Pine, Elm, Mutt, mailx, Z-Mail, fetchmail, Netscape Communicator, mh Macintosh: Eudora, Netscape Communicator, Pegasus Mail, Z-Mail, MS-Internet Mail, POPMail II
When I try to set up my email software, I see all these strange acronyms! What are they and how do I make use of them?
In setting up almost any email software you will need to provide some basic information so that the mail software will know where to go to retrieve your mail and where to deposit your outgoing mail. Here are some of the basic terms that you are likely to see.
SMTP Server
The SMTP (Simple Mail Transfer Protocol) server or host refers to the computer system that will first receive your outgoing email before it sends it out to its destination computer. For this reason it is also sometimes referred to as the outgoing mail server. You usually will supply a computer name in domain name format to this parameter.
POP3 Server
The POP3 (Post Office Protocol Ver. 3) server or host refers to the computer system that stores any incoming mail for you under your email name so that you can pick them up (download) later. For this reason it is also sometimes known as the incoming mail server.
IMAP Server
Some email packages also support the newer IMAP4 (Internet Mail Access Protocol Ver 4) protocol for mail retrieval. IMAP has better and more features than POP3 but in order to use this, your Internet Service Provider (ISP) has to support this too.
News/NNTP Server
Some email software comes with the ability to access the Internet discussion groups/forums or Usenet. If that is the case and if you want to use it to access Usenet, you have to set the name of the news or NNTP (Network News Transfer Protocol) server. Note that this setting is not required if you just want to use the email features of your software.
Can I download my mail and still keep them on the POP3 server?
Yes you can, since in most email software there should be an option to not delete the mail after downloading them from the POP3 server. However, it is probably not a good idea to make this the default option since leaving them on the server will take up hard disk space on the server and most ISPs provide a limited amount of disk space for a subscriber's mailbox, usually a few megabytes. It will not be able to receive any more email until you free up some space.
Can I selectively download my mail messages from the POP3 server?
You can if your email software allows this. However this feature is usually not implemented in most of the email software in common use. Normally you will have to download all the unread messages in one go. The IMAP4 protocol provides more features in terms of mail messages management on the server.
Can I send and receive my email from different computers in different physical locations?
You should be able to do that as long as the computers have access to the Internet and the mail protocols (i.e. SMTP, POP3/IMAP4) are allowed to pass through from the network that the computers are on to the Internet. Note that you may have to reconfigure the email software on the system that you are temporarily using to access the correct servers for sending and receiving mail. If you are using POP3 to retrieve mail, also note that unless you have configured the POP3 setup on the temporary computer not to delete mail after download, your mail will be deleted and you will not be able to retrieve the downloaded messages when you get back to your normal computer.
Can I use my web browser to send and receive email?
What is web-based email? Web-based email makes use of the web browser as the user interface to composing, reading, sending and maintaining your email messages. If you have access to a web-based email site., you can then send and receive email using the web browser. There are many such sites on the Internet, e.g. www.hotmail.com, www.email.com, webmail.netscape.com, mail.yahoo.com, www.maxis.net, which provide free web-based email account.
The main advantages of web-based email are:
1) It uses the familiar web browser for composing, sending and receiving email.
2) You can access your mail from anywhere as long as you have a web browser and Internet WWW access.
3) You can manage your mail messages on the remote web-mail server, e.g. deletion, move into new folders etc. Since the messages are all stored on the server and not automatically downloaded to you PC when you read your mail, a consistent state of your email is maintained even if you access it many times from many different locations.
The main disadvantages of web-based Internet email are:
1) Access to the web mail server can be slow.
2) Since all the email messages are stored on the web mail server in your mailbox until you physically delete them, care has to be taken to see that you do not fill up your mailbox.
3) Free web-based email usually have advertisements displayed together with your mail messages.
4) How can I send non-text email?
Traditionally Internet email uses only text-based messages. However with the widespread adoption and use of Internet email as a means of communication for both personal and business purposes, it has become very common to send non-textual information via email. These include word processing, spreadsheet, database and business presentation files. These are usually sent as file attachments.
Note  that the datafiles produced by OA packages can be very large, especially if graphics and multimedia are involved. As such if you need to send these files via email, you should compress them first so as not to cause unnecessary congestion on the Internet. The receipient of the email will also appreciate this if she is using a slow Internet link.
How can I open attachments received with my email?
That depends on how your system has been configured. Sometimes it can automatically run the application required to view the attachment file but if it cannot, then normally you will have to save it as a separate file on your computer and then physically invoke the appropriate application to view it.
How can I send mail messages with full text formatting?
Many PC-based email software nowadays support composing an email message in HTML (the language of the web) format and so with this, one is able to perform full text formating on a mail message, e.g. various fonts, color, highlight, tables etc. However you should refrain from doing this unless you are aware that the receipient can read HTML messages properly. There are also some security considerations if you allow reading of HTML-formatted email. (See the questions below.)
Can I send and read web pages (HTML formatted messages) with my email?
You can if your email software can support this. However it is not a good idea to make this the default format for the email messages that you send out. Please bear in mind that there are many email users on the Internet who are using software that cannot display HTML messages. You should also refrain from setting your email software to send both HTML and non-HTML messages since this will result in an email message being more than twice as long.
Can my computer be infected with a virus from my email?
The act of reading a plain email message cannot infect your computer with a virus (assuming that the email software used is written properly). However it is possible for an email message to carry with it a virus-infected file, especially in the form of an executable attachment (e.g. EXE, COM or macros). Then when the file is executed the virus will be activated. Thus you should carefully check executable files (including wordprocessing and spreadsheet files which can run macros) received via email with a virus scanner before running them. Having said the above, it should be noted that the growing popularity of HTML email messages which can incorporate programming languages like Java, Javascript, VBScript, etc. in them has made it more feasible for a malicious HTML rendered email message to perform nasty things, just by opening it up and reading it with HTML enabled on your email reader. Also, if one is on the Windows platform, by default MSWindows allows the automatic execution of certain file types which can contain embedded scripts like Visual Basic scripts from your email software like Outlook Express and Eudora. So a malicious email can contain either attachments or specially crafted HTML-formatted messages which under certain conditions can be made to run just by reading the messages or looking at the preview window for the attachment. In fact there is a new breed of viruses and worms making the rounds that spread by exploiting this "feature" of Windows and Internet email.
What is a mailing list?
A mailing list is an email alias specifying the email addresses of multiple recipients. When a message is sent to the list, a copy of the message is delivered to each recipient on the list. Mailing lists provide a very simple and efficient way to share and disseminate information on the Internet for a group with similar interests.
What is an list server?
A list server is a program that maintains electronic mailing lists. The use of a list server makes it possible to automate the message delivery and management of a mailing list which may contain hundreds of thousands of addresses.
What is UBE? What is spamming?
Unsolicited Bulk Email, or UBE, is Internet email that is sent to a group of recipients who have not requested it.
Spamming generally refers to the act of sending UBE although the term "spam" encompasses a wider range of intrusive transmissions e.g. Usenet news postings, in which the same posting is cross-posted to many newsgroups. A spam is the Internet equivalent of junk mail. Spams are usually unsolicited advertisements sent to tens of thousands of users at once.
How did the term spam originate?
Remember the "Monty Python's Flying Circus" TV series of the sixties? The term spam comes from there. There was this sketch in that series whereby the waitress said "... well there's egg and bacon; egg, sausage and bacon; egg and spam; bacon and spam; egg, bacon, sausage and spam; spam, bacon, sausage and spam; spam, egg, spam, spam, bacon and spam; spam, spam, spam, egg and spam; spam, spam, spam, spam, spam, spam, baked beans, spam, spam, spam and spam; or lobster thermidor aux crevettes with a mornay sauce garnished with truffle pate', brandy and a fried egg on top of spam." Meanwhile, in the background, a group of Vikings randomly sang the "spam" song. (I suppose you really have to be a Monty Python fan to understand and appreciate all this!)