You don't want to send a 20MB video directly as an email attachment unless you know specifically the email service your recipient is using can handle it. Different email services have different file size limitations -- Gmail is 25MB while Juno has a variable limit of 10MB (for its free service) to 30MB (for its highest level of pay-for accounts). Size limitations vary widely for a lot of reasons so it's a big variable, especially if you're sending it out to multiple people using the endlessly different email services available.
A much more consistent and reliable way to share videos is to upload them to an online storage account (Google Drive, SpiderOak, Dropbox, MS OneDrive, etc.) and then just email the shareable link to that video. You're probably better off uploading things like videos to an online account anyway, it's important to have some kind of backup.