Stamped.io runs on top of SendGrid which supports full DMARC compliance.
Contact Stamped.io support for DKIM setup. For general information, visit: https://stampedsupport.zendesk.com/hc/en-us/articles/9521862912539-SPF-DKIM-Records
Contact Stamped.io support for SPF setup. For general information, visit: https://stampedsupport.zendesk.com/hc/en-us/articles/9521862912539-SPF-DKIM-Records