Thanks for you hints! So far I have managed to create a new message with the listet source code.
However I cann talter the contents of the original message. Here is my code:

‘ Create a draft message and set the subject and body text
Set oDraftMsg = oFolder.Messages.Add(fgwDraft)
oDraftMsg.subject.plaintext = oMsg.subject.plaintext
oDraftMsg.BodyText.PlainText = oMsg.BodyText.PlainText & vbCrLf & “Attached files saved to:” & vbCrLf & AttachFileName
oDraftMsg.BodyText.RTF = oMsg.BodyText.RTF & vbCrLf & “Attached files saved to:” & vbCrLf & AttachFileName

‘ Setup the recipients
for x = 1 to oMsg.Recipients.count
set oRecipient = oMsg.Recipients.item(x)
call oDraftMsg.Recipients.Add(oRecipient.EmailAddress,,oRecipient.TargetType)
set oRecipient = nothing

set oNewMsg = oFolder.Messages.AddExistingMessage(oMsg.Sender.DisplayName, oMsg.Sender.EmailAddress, oMsg.Sender.EmailType, oMsg.CreationDate, oMsg.BoxType, 1, oMsg.Priority, 0, oDraftMsg, oMsg.ModifiedDate)

What ever I try the message text remains unchanged. Secondly the resulting message is only plain text (no more HTML).

What am I doing wrong?