This looks like upstream bug https://bugzilla.mozilla.org/show_bug.cgi?id=92111 right?
In short, as far as I understand: * Strictly spoken it's a bug in Exchange * You can configure Exchange to do the right thing using the configuration at http://support.microsoft.com/kb/191504 * You can work around it at the client side by setting mail.server.default.mime_parts_on_demand to 'false' as described at https://bugzilla.mozilla.org/show_bug.cgi?id=92111#c94 -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org