Rudi, from what I have experienced with SAP Business Connector 4.6 (same as B2B Integration Server 4.6 I believe), if the sending mail client has encoded the email as a multipart/mixed message (i.e. multiple MIME payloads in the same email), each part is extracted by the content handler and passed to an independent invocation of the service attached to the email listener. What this means is that the body of the email is passed to your service as an attachment (although it may contain other artifacts).
If this is the case in the WebMethod’s version of this software, you may be able to extract the body text data in the same way as you do an attachment, although you may need to do some parsing of the information returned. If this works then the only other thing you need to take care of is terminating the service prematurely if the “attachment” you get is not the body text e.g. if someone using MS Outlook formats the email using HTML, you will get additional invocations of the service which try to process other “invisible” attachments such as GIF files etc.
Hope this is of some use to you.
#webMethods#webmethods-Protocol-and-Transport#Integration-Server-and-ESB