I recently cannot open attachments in my yahoo mail. I have Adobe and can open existing attachments from non-email files. I am a musician and get sent music and program pdfs, but when I try to download and save to computer, a tab appears at bottom left that briefly looks like an "attempt" but then only says javascript which flicks from left to right if I move the mouse to it.
Hotmail / Outlook.com blocks unsafe attachments and some file name extensions.
If you need access to an attachment that Outlook won't let you download trying installing Windows Live Mail and using that mail program on your computer to get the attachments.