When Exchange 2000 is installed, it extends the features of the SMTP service and adds new components through the use of transport and protocol event sinks. Some of the key extensions that Exchange 2000 adds to SMTP are:

• Command verbs that support link state information
• An advanced queuing engine
• An enhanced messaging categorisation agent

Exchange 2000 enhancements to the SMTP service are described by the following

• SMTP Protocol Engine (Smtpsvc.dll )
• ImailMsg
• Store Drivers
• Advanced Queuing Engine
• Message Categorizer
• Routing Engine