input: 
  def validate_mail_list(mail_list: List[str]) -> bool:
      """
      Validate a list of email addresses to ensure that each one is in a valid format.
      An email is considered valid if it contains only one '@' symbol and at least one
      dot after the '@' symbol.
      >>> validate_mail_list(["example.user@gmail.com", "bad@example"])
      False
      >>> validate_mail_list(["user@domain.com", "another.user@example.org"])
      True
      """
  
output:     for email in mail_list:
          if email.count('@') != 1:
              return False
          at_index = email.index('@')
          if '.' not in email[at_index:]:
              return False
      return True