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Nework Services: E-mail
E-mail, too, is a network service that operates according to a client-server scheme.
A mail server computer performs several key functions:
- A mail server
takes care of sending outgoing e-mail to other mail
servers and receiving incoming e-mail from other mail
server computers. This exchange of e-mail between e-mail servers happens
according to the SMTP protocol.
- A mail server
handles requests from mail client software seeking
to send mail. This communication between server and
a client wishing to send mail also happens according to SMTP
- It is a
weakness in the SMTP protocol that can enable the "spoofing"
of e-mail addresses when sending mail—i.e., sending e-mail
as someone other than yourself.
- It is a
weakness in the SMTP protocol that can enable the "spoofing"
of e-mail addresses when sending mail—i.e., sending e-mail
as someone other than yourself.
- A mail server
processes requests from clients wishing to read mail
received from other mail servers. This communication between server
and a client wishing to receive mail happens according to one of two
protocols:
- POP
("Post Office Protocol"—not "point of presence"!);
- IMAP
("Internet Message Access Protocol").
Both POP and IMAP are very commonly used. However, POP clients send a user's password to the mail server in "plain text," unencrypted. Thus, this poses a security risk. IMAP, on the other hand, allows a user to specify that the mail client should send the password in encrypted form.
IMAP also offers a number of extended features, including the ability to view portions of incoming e-mail messages while they are still on the server. Thus, a user can first check if there is any urgent e-mail on the server before deciding whether or not to take the time to download messages from the server to the client.
Remember: POP and IMAP are only used to receive messages from the mail server. A mail client is typically still required to use SMTP commands in order to send e-mail. - POP
("Post Office Protocol"—not "point of presence"!);
There are a great
variety of e-mail clients available today. One of the most common is Microsoft's
Outlook Express. However, this e-mail client has repeatedly demonstrated
that it is not consistently secure in its operations, and very prone to
e-mail viruses.
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This chapter was written by Jeff Nyhoff and Joel Adams. Copy editing by
Nancy Zylstra
©2005 Calvin University (formerly Calvin College), All Rights Reserved
If you encounter technical errors, contact computing@calvin.edu.