[exim] DMARC / Abuse

Everyday, my abuse mailbox is filled with messages from Microsoft, Google
and Yahoo (MGY) reporting that others have sent suspicious emails using our
domain.

We have SPF & DKIM configured, not sure what if anything I should do with
these messages from MGY.

What do you do with this information? Our primary domain is katy.com I
believe we have it properly configured...perhaps not.