- These event interfaces are available on Windows SMTP servers as well as Exchange 2000 and 2003 servers. Exchange is not required to implement these events.
- These events may fire for internal messages when an event sink is configured on an Exchange server however, the event sink will not be able to modify messages submitted by MAPI clients as Exchange merely provides a copy of the message to the event sink - modifying this copy will not modify the message in the store.
- I your looking for working with a message in transport then look into Exchange Transport Agents, EWS Notification and DLP.
SMTP Server Events for Windows 2000
The Advanced Queuing Engine - TechNet provides a great run through of the delivery process and when the transport events fire...
SMTP Protocol Events
SMTP Transport Events
You cannot modify MAPI messages that are trapped in an SMTP transport event sink
Writing Managed Sinks for SMTP and Transport Events
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