1) At the moment, anyone can signup with any kind of email address (no confirmation required) and get access to my content/product/service.
2) I require members to signup before they can get access to my content. If they can add a fake email, that completely invalidates the "gate" in "gated content." It's also important when sending out required emails like Terms of Service updates.
3) There are some hacky workarounds https://community.memberstack.com/c/community-support/email-verification-process
4) Enable an optional email verification step. Let me use my own email verification emails. Let a service like Mailchimp verify emails.