@contextmanager
def smtp_connection(host, user=None, passwd=None, timeout=5):
    conn = None # smell here
    try:
        conn = SMTP(host=host, timeout=timeout)
        conn.ehlo_or_helo_if_needed()
        if user and passwd:
            conn.login(user=user, password=passwd)
        logger.debug('SMTP connected')
        yield conn
    except Exception as e:
        raise e
    finally:
        if conn: # and here
            conn.quit()

with ExitStack() as stack:
    stack.callback(cleanup_resources)
    result = perform_operation()
    if result:
        stack.pop_all()