Malformed emails, where multipart/alternative parts are embedded in a multipart/related part not displayed correctly

Malformed emails, where multipart/alternative parts are embedded in a multipart/related part are not displayed correctly. I have received such emails from various online services, included the largest search engine/webmail/map service in the Czech Republic Seznam such as the one enclosed. When you look at the structure it will be obvious how the message should be handled (and most email clients including Apple Mail) do display it as if it was formed correctly.