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|| The TCP/IP Guide|
9 TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
9 TCP/IP Key Applications and Application Protocols
9 TCP/IP File and Message Transfer Applications and Protocols (FTP, TFTP, Electronic Mail, USENET, HTTP/WWW, Gopher)
9 TCP/IP Electronic Mail System: Concepts and Protocols (RFC 822, MIME, SMTP, POP3, IMAP)
9 TCP/IP Electronic Mail Access and Retrieval Protocols and Methods
9 Other TCP/IP Electronic Mail Access and Retrieval Methods
TCP/IP Direct Server Electronic Mail Access
(Page 1 of 2)
In my overview
discussion of e-mail message communication,
I discussed the different devices involved in a complete mail exchange,
and how a message is created and then transported from the originator
to the recipient. SMTP is used to carry the message most of the way,
to the recipient's mailbox. The last step of the process is to convey
the message from the server where the mailbox is located to the machine
the client is using.
This final portion of the e-mail
journey is usually the job of an e-mail access and retrieval protocol
These are customized protocols, by which I mean that they were
created specifically for the last step of the e-mail communication process.
However, there are also several generic methods by which an e-mail
client can gain access to a mailbox, without the use of a special protocol
E-Mail Direct Access Methods
These methods are all variations
of the online e-mail
access model. They generally work by establishing
direct access to the server where the mailbox is located. The
mailbox itself is just a file on a server somewhere, so if that file
can be made available, it can be viewed and manipulated like any other
file using an e-mail client program that reads and writes the mailbox
file. The following are some of the ways in which this can be done:
- Using The SMTP Server Directly: Obviously,
the simplest method for gaining access to the mailbox is to simply log
on to the server itself. This is not an option for most people, and
even in years gone by it was not often done, for security reasons as
well as others. However, even today there are some people who do run
their own SMTP servers, giving them considerable control over access
to their e-mail.
- File Sharing Access: Using a protocol
such as the Network
File System, it is possible to have a
mailbox mounted on a user's client machine where it can be accessed
as if it were a local file. The mail is still on the server and not
the client machine, but the communication between the client and the
server occurs transparently to both the user and the e-mail
- Dial-Up Remote Server Access: A user on
a client machine dials up a server where his or her mailbox is located
and logs in to it. The user then can issue commands to access mail on
that server as if he or she were logged in to it directly.
- Telnet Remote Server Access: Instead of
dialing in to the server, a user can connect to it for remote access
using the Telnet Protocol.
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The TCP/IP Guide (http://www.TCPIPGuide.com)
Version 3.0 - Version Date: September 20, 2005
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