import re


def check_domain_valid(submission):
    """
    Check if a submission is a valid domain.

    :param submission: The submission to be checked
    :return: True if 'submission' is a valid domain, otherwise False
    """
    return re.match("^([A-Za-z0-9-]+(?:\\.[A-Za-z0-9-]+)*(?:\\.[A-Za-z]{2,}))$", submission) is not None