Emails are blank and black when I try to email them

Anytime I try to email a video I've taken with my digital camera, it is blank and black. I've tried a couple of free tiral programs I found via old forum suggestions to similar problems but they didn't work. I converted my files to a few different formats and still- blank and black. I cannot figure out why this is a problem. I use iphoto to store pictures and I use the mail program on mac. Could using Mail be the issue? I tried sending them from my email host website and it only changed how long the videos are.

I used a point and shoot camera and then I tried a video taken with my canon rebel - both of which use different formats. Still no success.

Has anyone else had and resolved this problem without investing in a converting software?