This sender is capable of DMARC compliance via both SPF and DKIM authentication.
DMARC compliance via DKIM is possible for users of Mimecast Gateway for outbound email. See https://community.mimecast.com/docs/DOC-1400#jive_content_id_Configuring_an_Outbound_DNS_Authentication_Definition
DMARC compliance via SPF is possible for users of Mimecast Gateway for outbound email. See https://community.mimecast.com/docs/DOC-2010