Exchange 2003 event sink to modify from adress doesn't work correc   

Hello,

I have an issue I can't explain to myself right now. I took a .vbs Script 
and registered it as an event sink in Exchange 2003 SP2 (SBS 2003) to modify 
the from address for a certain sender. 

It is working so far that the address is being replaced, but there ist an 
additional term saying "support1@something.de on behalf of 
support@something.de" in the address field.

So I guess Exchange is altering the message after the Event Sink. Why is 
that and how can I get around it?

The Script looks like this:

'<SCRIPT LANGUAGE="VBScript">
Option Explicit

'-------------------------------------------------------------------------
' FromModify.vbs
'
' Description: Modifies the "FROM" Address in the Header"
' Smaple to remove "DisplayName"
' Smaple to replace FROM-Address
'
' Runtime Errors are not handled
'
' (c)2006 Frank Carius. www.msxfaq.de
'
' Version 1.0 (14. Aug 2006) Frank Carius
'
' For information about this namespace, see
'   
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cdosys/html/_cdosys_schema_smtpenvelope.asp
' For information about the CdoEventStatus enumeration, see
'   
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cdosys/html/_cdosys_cdoeventstatus_enum.asp
' urn:schemas:mailheader: Namespace
' 
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cdosys/html/dbca4fb9-afcb-4716-9e0c-4bff45ca0b60.asp'
' The Advanced Queuing engine
' 
http://www.microsoft.com/technet/prodtechnol/exchange/guides/E2k3TechRef/eaad59e4-ccbe-4ebf-ac14-69264b1cc167.mspx?mfr=true
'
' Does NOT Work for Messages qued by MAPI. Has to be SMTP, OWA, ActiveSync 
or use a second SMTP as relay
'-------------------------------------------------------------------------

Const CDO_RUN_NEXT_SINK = 0
Const logfile = "D:\FromModify.log"
Const Loglevel = 5

Sub ISMTPOnArrival_OnArrival(ByVal Msg, EventStatus)
'	On Error Resume Next
	Dim objFields, strFrom

	AppendLog "-- FromModify START -----", 4

	AppendLog "load Message Properties", 5
	AppendLog " msg.from    :" & msg.from, 5
	AppendLog " msg.to      :" & msg.to, 5
	AppendLog " msg.subject :" & msg.subject, 5
	
	AppendLog "---- Processing FROM -----", 4
	strFrom = msg.from
	AppendLog " FROM (original): " & strFrom  , 5

	' This line removes everything in front of the "<"-Character
	'strfrom = mid(strfrom,instr(strfrom,"<"))
	'AppendLog " FROM (StripDisplayname): " & strFrom  , 5

	' This part replaced the FROM Address in the Header
	if instr(lcase(strfrom),"support1@something.de")>0 then strfrom = 
"""Support"" "
	AppendLog " FROM (modified): " & strFrom , 5

	msg.from = strFrom	
	Msg.Datasource.Save  ' save changes to the mail

	AppendLog "-- FromModify END -----", 4
	EventStatus = CDO_RUN_NEXT_SINK
End Sub


Sub AppendLog(strLog, errlevel)
	'Add an entry to the protocol and debugging log file
	Dim file
	Dim fs

	if loglevel>=errlevel then
		Set fs = CreateObject("Scripting.FileSystemObject")
		Set file = fs.OpenTextFile(logfile, 8, true)
		file.Write(Now & ",")
		select case errlevel
			case 1	file.Write("Fatal Line" & err.Source)
			case 2	file.Write("Error")
			case 3	file.Write("Warning")
			case 4	file.Write("Information")
			case 5	file.Write("Debug")
			case else file.Write("Code:"&errlevel)
		end select
		file.WriteLine(","&strLog)
		file.Close
	end if
End Sub

'</SCRIPT>

Regards,

Phil

date: Tue, 18 Mar 2008 02:52:00 -0700   author:   Jan-Philipp Wagner