I’m often receive emails with autocad dwg files. When I’m open such messages I’m see correct file name and extension. When I’m trying to save or open this files it offer to save as attachment.bin or specify program to open it.
It’s a wary big problem for me. Please fix it.
Otherwise there no sense to use your program.
I also get this problem. It only happens for a single sender, but happens every time. The file is HTML (named and displayed as whatever.htm), but opens/downloads as attachment.bin. If I log into webmail, the attachment is correctly handled.