Regexp to validate emails in Ruby

ValidateEmail.rb

# Strictly adhere to email address standards and disallow hyphens at the beginning or end of the domain name.
# Use https://rubular.com for live testing.

def validate_email(string)
      (string.downcase =~ /\A[a-zA-Z0-9._%+-]+@[a-zA-Z0-9](?:[a-zA-Z0-9\-_]*[a-zA-Z0-9])?(?:\.[a-zA-Z0-9]*)(?:\.[a-zA-Z]{2,})+\z/)&.zero?
end