Your main point of entry for email within your organization might be an SMTP server behind a hardware firewall. The SMTP server might be running the Windows 2000 SMTP service, or it might be an Exchange 2000 Server front-end server in a front-end/back-end architecture. Either way, the Win2K SMTP service provides another solution point for content management through a third-party application or a custom solution. The key in an SMTP solution is to make use of transport events.
When the SMTP service transports a message into or out of a service, a transport event fires. You can configure the SMTP service to hold the message until your custom code has used a transport event sink to process the message before relaying it to the recipient. This process is called synchronous mode because no other processing can continue until the code runs. Your code has access to all parts of the message and can modify the body object (e.g., by adding a disclaimer to certain outgoing messages). The Microsoft article "SAMPLE: How to Add a Disclaimer to Outgoing SMTP Messages with SMTP Transport Events" (http://support.microsoft.com/support/kb/articles/q288/0/98.asp) illustrates how this process works.
Your code can be in any programming language or scripting language that supports COM, but for best performance you need to build event sinks by creating DLLs in either Microsoft Visual C++ (VC++) or Visual Basic (VB). This technique works for both the Win2K SMTP service and the Exchange 2000 SMTP service. For more information and sample code, see the Exchange 2000 software development kit (SDK) at http://msdn.microsoft.com.