The Message Is the Medium: Selecting a Mail System - Page 3

By Hallett German | Posted Dec 27, 2002
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In its simplest form, a messaging system allows two users to send and receive written communications from each other. Two hardware/software components are involved, the client program or message receiver and the server or message transport mechanism:

  • The client downloads e-mail and allows the user to read messages on their local machine. The messaging client ideally should be available across hardware and software platforms for reduced maintenance costs

  • The server relays e-mail from other servers and oversees the downloading of messages to the client. E-mail systems all use a "store and forward" system of transport.

Regardless of which messaging system you select, it will need to incorporate Internet messaging standards. Internet messaging standards address the following seven challenges:

Challenge 1: Sending a non-text or "complex" message. MIME (Multi-purpose Internet Mail Extensions) was created to handle complex messages. This complexity may refer to attachments (sounds and movies), different languages, or different hardware/software platforms. The basic Internet message standard is described in RFC 822, also known as "rfc822 format." A coding mechanism named base64 is used to encode attachments. Here is a typical text MIME header:

Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"

The header information includes the MIME version, a type of text and a subtype of plain. It also tells you that the US ASCII character set is used. The sample has only the bare minimum of information that can be incorporated. Common MIME types include text, image, audio, video, and application (which would include binary files and Postscript files).

Challenge 2: Messaging and security. Most messaging clients support S/MIME (Secure Multipurpose Internet Mail Extensions) an Internet standard developed by RSA to handle privacy, data integrity, and authentication. It sends secure e-mail using digital signatures and encryption.

Challenge 3: Sending mail between local clients. There are three types of relationships between servers and clients:

  • Online -- Messages are left on the server where they can be accessed and manipulated by one or more users.

  • Offline -- Messages are downloaded from the server and placed on the client device.

  • Disconnected -- A copy of the messages are downloaded from the server to the client. However, a copy of the messages remains on the server. The client periodically connects with the server to catch up with new messages.

The two commonly used Internet mail standards are POP and SMTP. POPMail or POP3 (Post Office Protocol, version 3) is simpler to maintain and the more popular of the two. POPMail supports offline mode and folder management (of one folder). IMAP (Internet Messaging Access Protocol) provides message management features closer to those found on many proprietary systems. IMAP supports offline mode, online/disconnected mode, folder management (multiple folders), and shared mailboxes (such as group messages, news groups, help areas).

Challenge 4: Moving mail from server to the Internet. SMTP (Simple Mail Transfer Protocol) uses the TCP/IP protocol to send text messages between servers (also called Message Transfer Agents, or MTAs) across the Internet.

Challenge 5: Overcoming SMTP limitations. SMTP has been around for close to 20 years so it has some limitations, so two protocols have been created to enhance SMTP functionality.

ESMTP (Extended SMTP) includes delivery service notifications (return receipt), enhanced error codes, and size limitations on large messages.

With ESMTP, you can block messages based on size, or forward a note back to the sender not to send large files again.

Challenge 6: Looking up the network addresses of the mail servers. DNS (Domain Naming Service) is a distributed database filled with resource records of public Internet servers (including mail servers) their names and IP addresses. The major implementation of DNS called BIND (Berkeley Internet Name Domain) includes records specifically used for mail transport.

Challenge 7: Looking up messaging recipients. Before LDAP (Lightweight Directory Access Protocol), the complexity of server setup and administration kept many companies from implementing electronic directories. Now LDAP has simplified things so that directories are available for messaging recipient lookup, authentication, and many other uses.

Conclusions
We have just touched the surface of the intricacies of messaging systems. At the end of the day, will the company be more productive with the new system? Only you can answer that for your company, but if you ask yourself a few simple questions to when evaluating systems, you will save yourself a lot of headache.

  • What are the business drivers for the new system?
  • Will the employees experience higher productivity and job satisfaction because to the better tools and integration with desktop applications?
  • What is the current and projected messaging traffic for the company?
  • How much training is needed to bring my users and administrators up to speed?
  • If we merge with another company, how easily can we consolidate both messaging systems?
  • How much time will my administrators be spending on firefighting with the new system? How much time on administration?

References
DNS Resources Directory
MIME FAQ
IMAP vs. POP
IMAP
Refrigerators with e-mail!
S/MIME
ESMTP
LDAP

Hallett German is an IT consultant who is experienced in implementing stable IT infrastructures with an emphasis on electronic messaging and directories. He is the founder of the Northeast SAS Users Group and former President of the REXX Language Association. He is the author of three books on scripting languages. Beth Cohen is president of Luth Computer Specialists, a consulting practice specializing in IT infrastructure for smaller companies. She has been in the trenches supporting company IT infrastructure for over 20 years in a number of different fields including architecture, construction, engineering, software, telecommunications, and research. She is currently writing a book about IT for the small enterprise and pursuing an Information Age MBA from Bentley College.


» See All Articles by Columnist Beth Cohen


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