What you will learn in this module:
- Overview of Microsoft Exchange Server 5.5
- Client-server based messaging systems compared with file based messaging systems
- Overview of supported standards
- Integration with other messaging systems
- Client support and client overview
- NT Administration tools
What is Exchange
Exchange Server is a Client/server based messaging system which delivers the following services:
- E-mail
- Scheduling
- Document Sharing
- Electronic Forms
- Custom Applications
It is now in it's fourth generation, if you count Exchange Server 2000. Exchange Server 5.5 offers a fully featured messaging system which can support small organizations (Small Business Server) at one end, and still scales really well for large organizations at the other (Enterprise Edition).
File Based Messaging Systems
In file based messaging systems, the following process takes place when a message is being sent and received.
- A client computer connects to a shared data area, and delivers the message into the appropriate folder for the recipient
- The recipient computer connects to the same server, and retrieves the message from their folder
This scheme has several advantages and disadvantages:
Advantages
- It is easy to maintain single-server file based messaging systems
- The server is basically a file store, and therefore does not need to be particularly powerful
Disadvantages
- Because of the way that clients deliver messages, it means that all clients (and hence users) have full access to all folders within the shared messaging folder. This is clearly undesirable
- There is little distribution of processing effort - the client systems do all the work; the servers just store the messages
- The load on the network is often higher as client systems continually poll the file server system to see if there are messages waiting in the client's folder
A good example of a file based messaging system is Microsoft's MS Mail program. Here client computers connected to a shared folder called MAILDATA.
Post Offices were linked together to create networks of messaging servers. The program used to connect the Post Offices was called External, and essentially had connections to the MAILDATA folders on several servers simultaneously.
Whilst MS Mail had limited scope for scaling to the enterprise, it didn't require a great deal of hardware to implement, and was relatively simple to maintain.
