Return a list of lists for the MX of ``domain``.

    If the 'resolve' argument is True, resolve IPs for the servers.

    It's limited to one IP, because although in practice it's very rarely a
    round robin, it is an acceptable configuration and pulling just one IP lets
    the data be similar to the non-resolved version. If you think an MX has
    multiple IPs, don't use the resolver here, resolve them in a separate step.

    CLI Example:

    .. code-block:: bash

        salt ns1 dnsutil.MX google.com

def MX(domain, resolve=False, nameserver=None):
    '''
    Return a list of lists for the MX of ``domain``.

    If the 'resolve' argument is True, resolve IPs for the servers.

    It's limited to one IP, because although in practice it's very rarely a
    round robin, it is an acceptable configuration and pulling just one IP lets
    the data be similar to the non-resolved version. If you think an MX has
    multiple IPs, don't use the resolver here, resolve them in a separate step.

    CLI Example:

    .. code-block:: bash

        salt ns1 dnsutil.MX google.com
    '''
    if _has_dig():
        return __salt__['dig.MX'](domain, resolve, nameserver)

    return 'This function requires dig, which is not currently available'