The e-mail server world is much more fragmented than the Web server world. The current leader is sendmail used on Linux and UNIX operating systems. Like Apache, sendmail doesn't really have an interface, but there are many different third-party interfaces to help configure sendmail, such as Webmin.
Sendmail controls about 20 percent of all e-mail servers, but only uses SMTP. You must run a POP3 or IMAP4 server program to support e-mail clients. Programs like Eudora's Qpopper handle sending mail to POP3 e-mail clients. Microsoft, of course, has its own e-mail server, Microsoft Exchange Server, and like IIS it only runs on Windows. Exchange Server is both an SMTP and a POP3 server in one package.
E-mail servers accept incoming mail and sort out the mail for recipients into individual storage areas mailboxes. These mailboxes are special separate holding areas for each user's e-mail. An e-mail server works much like a post office, sorting and arranging incoming messages, and kicking back those messages that have no known recipient.
Perhaps one reason e-mail servers are so little understood is that they're difficult to manage. E-mail servers store user lists, user rights, and messages, and are constantly involved in Internet traffic and resources. Setting up and administering an e-mail server takes a lot of planning, although it's getting easier. Most e-mail server software runs in a GUI, but even the command-line-based interface of e-mail servers is becoming more intuitive.
E-mail Client An e-mail client is a program that runs on a computer and enables you to send, receive, and organize e-mail. The e-mail client program communicates with the SMTP e-mail server to send mail and communicates with the IMAP or POP e-mail server to download the messages from the e-mail server to the client computer. There are hundreds of e-mail programs, some of the most popular of which are Microsoft's Windows Mail, Microsoft Outlook, Mozilla Thunderbird, and Qualcomm's Eudora.
Configuring an E-mail Client Configuring a client is an easy matter. Your mail administrator will give you the server's addresses and your mailbox's user name and password. You need to enter the POP3 or IMAP4 server's IP address and the SMTP server's address to the e-mail client. Every e-mail client has a different way to add the server IP addresses, so you may have to poke around, but you'll find the option there somewhere! In many cases this may be the same IP address for both the incoming and outgoing servers?the folks administering the mail servers will tell you. Besides the e-mail server addresses, you must also enter the user name and password of the e-mail account the client will be managing.
In this tutorial:
- TCP/IP Applications
- Transport Layer Protocols
- The Power of Port Numbers
- Registered Ports
- Connection Status
- Rules for Determining Good vs. Bad Communications
- Common TCP/IP Applications
- Publishing Web Pages
- Web Servers and Web Clients
- Secure Sockets Layer and HTTPS
- Telnet Servers and Clients
- Configuring a Telnet Client
- Rlogin, RSH, and RCP
- SSH and the Death of Telnet
- SMTP, POP3, and IMAP4
- Alternatives to SMTP, POP3, and IMAP4
- E-mail Servers
- Passive vs. Active FTP