Yes, indeed your right this is actually a problem in ACS. Sorry for that.
I'm using Alfresco version 5.2.1. What do you mean by "what type of email" these are mails that can be send to a specific address and these are redirected to a folder in Alfresco where the files are visualised and threaded by an external application. In my test case the mail was sent from Outlook. I retries right now and the field "cm:addresse" just contains the address for alfresco. As I can see in the source code you sent there seems to be another field "toNames". Is it possible to access this? It seems not to be listed when I look at the properties of the document?