code: func validateEmail(address string) error {
  	email, err := mail.ParseAddress(address)
  	if err != nil {
  		return unparseableEmailError
  	}
  	splitEmail := strings.SplitN(email.Address, "@", -1)
  	domain := strings.ToLower(splitEmail[len(splitEmail)-1])
  	if forbiddenMailDomains[domain] {
  		return berrors.InvalidEmailError(
  			"invalid contact domain. Contact emails @%s are forbidden",
  			domain)
  	}
  	if _, err := iana.ExtractSuffix(domain); err != nil {
  		return berrors.InvalidEmailError("email domain name does not end in a IANA suffix")
  	}
  	return nil
  }
docs: // validateEmail returns an error if the given address is not parseable as an
  // email address or if the domain portion of the email address is a member of
  // the forbiddenMailDomains map.