Monitoring event sink # 20 – MailMsg COM class


MailMsg – COM Class


The MailMsg COM class represents a message as it proceeds through the SMTP service.



  • The information within the MailMsg object is persisted to some physical location such as the file system using objects and file handles provided by the installed store driver object.

  • The MailMsg COM class is integral to the SMTP service and does not need to be implemented.

  • Transport and protocol event sinks use references to a MailMsg object to access information about the message and the message contents as it proceeds through the service to its final destination.

MailMsg – CoClass 


CLSID : 39b16f50-a8ba-11d1-aa91-00aa006bc80b


ProgID : Exchange.MailMsg


Inproc Server : %SystemRoot%\System32\inetsrv\mailmsg.dll


Available Interfaces:



For more detailed information, please read this article.