DMARC compliance possible via SPF and DKIM. More on HappyFox and DMARC: https://support.happyfox.com/kb/article/499-how-to-configure-dmarc-and-spf-for-your-domain-to-use-with-happyfox/
For more information visit: https://support.happyfox.com/kb/article/1096-dkim-for-outbound-emails/
Add 'include:spf.happyfox.com' to your SPF record. For more information visit: https://support.happyfox.com/kb/article/294-using-spf-records-to-aid-proper-email-delivery/