The purpose of one of our projects was MS Exchange handler for processing incoming email.

The basic source of knowledge was this article "Developing Managed Event Sinks/Hooks for Exchange Server Store using C#" by Logu Krishnan, published to the address http://www.codeproject.com/csharp/CsManagedEventSinksHooks.asp , and also examples from Microsoft Exchange SDK.

We utilized Synchronous Events and created the handler, which fires on OnSyncSave event. The handler creates activity record in Microsoft CRM and then removes the message in the Exchange database before the commitment:

public void OnSyncSave(IExStoreEventInfo pEventInfo, string bstrURLItem, int IFlags)
{
try
{
if (IFlags == ((int)EVT_SINK_FLAGS.EVT_SYNC_COMMITTED + (int)EVT_SINK_FLAGS.EVT_IS_DELIVERED))
{
ProcessMessage(pEventInfo, bstrURLItem, IFlags);
}
}
catch (Exception ex)
{
log.Debug(ex.Message + "\n" + ex.StackTrace);
}
finally
{
LogManager.Shutdown();
}
}

For Exchange handlers debugging - it is the extremely convenient to use system log4net in RollingLogFileAppender or RemoteAppender modes (for multiple instance of COM + objects). You can read more on this subject here http://logging.apache.org/log4net/

To allow the handler incoming mail removal, it is necessary to give proper rights to the user, under which account the COM+ application runs the handler. These are rights on change of the information in user's boxes for whom it is registered (Windows 2003 Server: Active Directory Users and Computer -> Users -> Properties (for COM+ application account) -> Exchange Advanced -> Mailbox Rights). And now the code:

private void DeleteMessage(string bstrURLItem)
{
try
{
ADODB.Connection oCn = new ADODB.Connection();
oCn.Provider = "exoledb.datasource";
oCn.Open(bstrURLItem, "", "", -1);
if(oCn.State == 1)
{
log.Debug("Good Connection");
}
else
{
log.Debug("Bad Connection");
}
ADODB.Record rec = new ADODB.Record();
rec.Open(bstrURLItem, oCn,
ADODB.ConnectModeEnum.adModeReadWrite,
ADODB.RecordCreateOptionsEnum.adFailIfNotExists,
ADODB.RecordOpenOptionsEnum.adOpenSource,
"", "");
rec.DeleteRecord(bstrURLItem, false);
rec.Close();
oCn.Close();
rec = null;
oCn = null;
}
catch (Exception ex)
{
log.Debug(ex.Message + "\n" + ex.StackTrace);
}
}

Happy customizing!