As we know from the web services attachments matrix, Wcf does not natively support Soap With Attachments (SwA, sometimes referred to as Mime attachments). Fortunately some nice people from Microsoft and SVC GmbH. in Austria have published a proof of concept for a Wcf SwA encoder. It does not have a fancy API yet and you would have to hard code your attachments in the encoder code itself. However it is a great start if you need such an interoperability.