I use gmail and I was doing some cleaning to get rid of past things I don't need anymore, until I saw this message:
I am sure that this file (which is a password protected rar archive) is safe and doesn't contain anything dangerous. And by the way I was able to download it in the past. But why is it now blocked? Because now gmail isn't happy with password protected archives. For your safety, of course…
I wanted to check my attachments, too: sometimes I use gmail to send to myself archives of things both in order to transfer them from a computer to another and to keep them in (another) “cloudy” place.
Some of them can't be downloaded neither. Most of them aren't password protected. They are just archives, but it happens they contain other (not password protected) archives. And this is another category now Google isn't happy with. Always for your safety…