The cause is, may be, in 'protected' declaration. I used private DataHandler stmtContent; @XmlElement(name = "StatementContent", required = false) @XmlMimeType("application/zip") public final DataHandler getStmtContent() { return this.stmtContent; } public final void setStmtContent(DataHandler stmtContent) { this.stmtContent = stmtContent; } and it works fine with .NET client. Another thing you can do: put into your endpoint declaration @MTOM(enabled = true) in addition to @BindingType View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4170061#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...