I received an excel file attached to an email from someone that I regularly receive files from. When I tried to open it a Microsoft notification box popped up saying the file was corrupt and couldn't be opened.

I tried saving the attachment to my laptop, but the same thing happened. Another person received the same file and they were able to open it.

I tried a little experiment. I sent myself one of my own files as an attachment to an email. I was not able to open the attachment - same corrupt file notice.

Any ideas as to what's going on?

I just upgraded my computer to Windows 10
I use Office 365