The issue is that MMS and iMessage aren't compatible. The "fix" id for someone to sit Tim Cook in an ice bath until he fixes that.
(If you've ever had an iPhone, make sure you took it off iMessage. If you no longer have one, someone at a Genius Bar can do it for you.)
Have each of your iPhone friends send you at least one message marked SMS, so their phones know to not be expecting iMessages from you.
And convert your videos to a format that an iPhone can play. (That's easier than having every one of them installing an app that can play the format you're sending them. (QuickTime is native Apple, so that should work.) Or they can install VLC, which plays almost anything. Just send them the URL https://www. videolan. org/vlc/download-ios. html (with the spaces removed - I didn't want toe site to crunch it up).