Our data indicates ESU6 supports DMARC compliance via SPF and DKIM.
Our data indicates a very small amount of traffic supporting DMARC-compliant DKIM signing. Contact ESU6 to ask about their DKIM capabilities.
Our data indicates data comes from '162.127.6.0/24' and '162.127.60.0/24', which translates to an addition of 'ip4:162.127.6.0/24 ip4:162.127.60.0/24' to your SPF record. In any case, be sure to contact ESU6 to verify this information and obtain a better authorization if available.