Topic Last Modified: 2009-03-16

The Microsoft® Exchange Server Analyzer Tool queries the Microsoft Internet Information Server (IIS) metabase to enumerate the list of Simple Mail Transport Protocol (SMTP) transport event sink bindings. The Exchange Server Analyzer attempts to locate a number of standard event bindings, based on a list pre-populated in the Exchange Server Analyzer. For each binding, the Exchange Server Analyzer verifies the Component Object Model (COM) registration details in the Registry under the following branch:


The Exchange Server Analyzer displays a warning if the following conditions are true:

An SMTP transport event occurs when message data is transported into or out of the SMTP service. All messages go through events. These include X.400 and RPC incoming or outgoing messages. One common example of an inbound transport event is the arrival of a message to the SMTP service either over the network or in the SMTP pickup directory. When this transport event occurs, a source for this event notifies the transport event sinks, each of which can take some type of action based on the data content of the message. The system performs no other action with the message data after it passes the message data to the sink until the sink completes its action and returns the message. The sink has exclusive control of the message data and state while it performs this action.

Missing COM registrations for transport event sink bindings can cause mail flow problems. If the Exchange Server shows symptoms of mail flow problems such as message queuing, reregister the transport event sinks.

To reregister the transport event sinks
  1. From the Microsoft Exchange Server, open a command prompt window and change to the \Program Files\Exchsrvr\Bin folder.

  2. Type the following commands to re-register transport event sinks:

    regsvr32 exps.dll

    regsvr32 miscat.dll

    regsvr32 onsubmit.dll

    regsvr32 peexch50.dll

    regsvr32 phatcat.dll

    regsvr32 protolog.dll

    regsvr32 reapi.dll

    regsvr32 regsinks.dll

    regsvr32 tranmsg.dll

    regsvr32 turflist.dll

    regsvr32 xlsasink.dll

    regsvr32 msgfilter.dll

  3. Rerun the Exchange Server Analyzer to verify that the warnings are no longer displayed. If event sink registration warnings continue and you experience mail flow problems, contact Microsoft Product Support Services (PSS).

For more information about transport event sink bindings see the following Exchange resources: