E-mail is a highly complex subject. This page only provides a simplistic overview of how e-mail works.

Overview.
Electronic Mail (E-mail) allows people or computers on a network such as the Internet to send each other messages.
A message written on one computer is passed from computer to computer until it arrives at its destination.
Computer files can be attached to an e-mail message, allowing easy exchange of files between two people or computers.

To read or send e-mail a person uses software called an e-mail client. E-mail clients allow you to compose, send, collect and read e-mail. Microsoft's Outlook and Outlook Express are examples of commonly used e-mail clients.

Individuals on a network are identified by an e-mail address which usually looks like username@domain, ie. support@vetsolutions.co.uk
Your Internet Service Provider (ISP) should provide you with e-mail addresses you can assign to people on your network for receiving mail from the Internet.

NB. As e-mail is transmitted as plain text files from computer to computer it should not be considered very secure.
A malicious third party with administrator access to any of the intermediate computers on the delivery route could easily read your mail. From a security perspective e-mail should be considered as secure as a postcard. It will probably not be read by others but you never know for sure. To make e-mail secure both the sender and recipient need additional software that encrypts (scrambles) messages before sending and decrypts (unscrambles) it before reading. This sort of software has to be configured on the individual computers that require secure e-mail and is beyond the scope of this document.

Terminology.

Mailbox : A mailbox is simply a place (usually a file or folder on a computer called a mail server) that stores the e-mail delivered to a specific person, until it is collected and read.

Local (or internal) e-mail is e-mail sent and received only by people on your local network. It should be dealt with internally (by an EnServe for example) and never involve the Internet.

Outgoing e-mail is e-mail sent from a person on your network to someone on another network, usually the Internet.

Incoming e-mail is e-mail sent to a person on your network from someone on another network, usually the Internet.

E-mail Aliases are essentially alternate or additional e-mail addresses for a person that are delivered to their usual mailbox.

Mail-servers are the computers that deal with moving (relaying) e-mail over a network and/or facilitate its collection.

SMTP is the Simple Mail Transport Protocol and is the standard used for sending e-mail around the Internet.

POP3 is the Post Office Protocol, the most common method of collecting e-mail from an Internet Service Provider.

E-Mail Client. An e-mail client is a piece of software that lets a person manage their e-mail. It provides the functionality required to send and receive e-mail through mail servers, read, organise and compose new e-mail and often much more.

Creating E-mail.
To create e-mail a program called an e-mail client is used. Outlook for Windows or Pine for Unix are common e-mail clients. Generally you just specify a recipients e-mail address, type a message then send the message.

E-Mail Delivery.
E-mail is generally moved around networks and the Internet using the Simple Mail Transport Protocol (SMTP). This is a set of rules that govern the way e-mail is delivered over a network. When the person sends an e-mail using their e-mail client the client's configuration tells it which mail-server to send the mail to. The client and the server negotiate the transfer of the e-mail from the client to the server using the rules provided by the SMTP.

Once the mail-server has received the e-mail it has to decide what to do with it. It checks the domain of the recipient's address. If that mail-server is responsible for mail to that domain it saves the e-mail to the appropriate person's mailbox or deals with it in some other way depending on the username part of the address.

If the mail-server is not responsible for e-mail addressed to the domain of the recipient address it can do one of two things depending on how it is set up.. It can try and find out what mail-server is responsible and pass it the e-mail using SMTP or it can just pass the message on to a another mail-server (know as a smart-relay) that can work out what to do with the e-mail. The e-mail may travel between many mail-servers before arriving on the one that is ultimately responsible for delivering that domain's e-mail. When the e-mail arrives on the destination mail-server it deals with the delivery of the e-mail to the user, usually by saving it to a mailbox for later collection.

To add an aliases, use the admin account, Administration Menu -> Edit System File -> Aliases.

The format of each entry is Alias a colon : followed by a list of the user(s) it goes to.

vets:       tmelvin, tom, andy
Tom.Melvin: tmelvin
T.Melvin:   tmelvin
All:        user1, user2, user3, user4,
            user5, user6 

It is a good idea to alias all the possible ways a users name could be spelt, in the above example, user tmenvin will get mail addressed to Tom.Melvin@domain, t.melvin@domain etc. you should also note case is not important on the users names, TMelvin, tMelvin, TMELVIN, tmelvin are all the same.

Add in you groups here as well, the above example has a group 'vets', any mail addressed to vets@domain will go to TMelvin, Tom and Andy. If you need to add a lot of users, then just leave some whitespace at the beginning of the line and it will be taken as a continuation of the previous one.

E-Mail Collection.
There are a few ways for a person to collect their E-Mail from their mailbox on a mail-server.
By far the most common method is to use an e-mail client to get the mail from the server using the Post-Office Protocol (POP3). POP3 is a set of rules governing the collection of e-mail from mailboxes. The e-mail client negotiates the transfer of the e-mail from the mail-server following the POP3 rules. This usually requires the passing of a username and password to identify the person and authorise their access to the mailbox.

The EnServe and E-Mail.
The EnServe can act as an incoming, outgoing and local mail-server for your network.
It can send mail from properly configured e-mail clients on your network directly to other mail-servers on the Internet or through a smart-host (also often called a smart-relay or mail-relay) provided by an ISP.
It can receive e-mail from one or more ISP's mail-servers using SMTP and/or collect it from multiple mailboxes using POP3.
The EnServe takes care of making sure e-mail is delivered to the right mailboxes for people on your network.
The EnServe can also scan all incoming e-mail for viruses and junk mail and deal with offending e-mail appropriately.