Our data indicates Tigron supports DMARC compliance via SPF.
Contact Tigron to ask about their DKIM capabilities.
All DMARC compliant traffic we've noticed comes from 'smtp0.web.tigron.net', which for the time being translates into an addition of 'ip4:86.39.66.57' to your SPF record. In any case, be sure to contact Tigron and verify this information.