Likely your video will be too large to send by email from your iPhone or your Mac.
Use the Air Drop feature on your Mac to send the video to the Photos app on your iPhone. First activate Air Drop on your iPhone Settings/General/Air Drop. You iPhone must be closer than 30 feet from your Mac.
When I want to share a video or a large group of photos or videos from my Mac, I use Google Photos. Create a Google Photos account, upload your photos or video to it, and then create a link to the photos or video that you want to send to others. You then can send the link by email to any recipients that you want. Remember to sign out from Google Photos after sending, or otherwise whoever opens the link will have access to your Google Photos account and all media stored in it.
I access Google Photos from my Mac, but I believe, but not sure, that you can also download it to your iPhone or access it from there. You'll need to check that out.
-- Rich