Trying to send a video but recipient can't open it...

I have an older video clip that someone made and sent to me years ago, they asked if I still had it and if I could send them the clip, I have it saved in my documents and it only says "Video" under the clip. I tried to send and forward the video back on facebook messenger and by email, the recipient says they can't open it. Am I sending this video wrong or is the recipient opening it wrong? I view this video on Media Player, do I have to change how it opens to my recipient when I send it? Can anyone help me out, thanks..