Anyone got any clues? I'm running 6.3, t-bird 10.0.12, and KDE. I get emails with .docx attachment, and t-bird has no idea what to do with them (and doesn't even offer me a choice)."Change your preferences... So I open the source of the email, and at the beginning of the doc I see Content-Type: application/vnd.openxmlformats-officedocument.wordprocessingml.document; In system settings->advanced->file associations, I see the applications/vnd... is set for libreoffice. T-bird is still clueless. mark