One of the largest providers we have seen that send malicious email in our DMARC reports is Digital Ocean

Putting DMARC in reject or Quarantine fixes this!

There IPs are listed below if you want to block these , and their ASN is 14061

Digitial Oceans IP Blocks

103.253.144.0/22 104.131.0.0/18 104.131.128.0/20 104.131.144.0/20 104.131.160.0/20 104.131.176.0/20 104.131.192.0/19 104.131.224.0/19 104.131.64.0/18 104.236.0.0/18 104.236.128.0/18 104.236.192.0/18 104.236.64.0/18 104.248.0.0/20 104.248.100.0/22 104.248.104.0/22 104.248.108.0/22 104.248.112.0/20 104.248.128.0/20 104.248.144.0/20 104.248.160.0/20 104.248.16.0/20 104.248.176.0/20 104.248.192.0/20 104.248.208.0/20 104.248.224.0/20 104.248.240.0/20 104.248.32.0/20 104.248.48.0/20 104.248.64.0/20 104.248.80.0/20 104.248.96.0/22 107.170.0.0/17 107.170.128.0/19 107.170.160.0/19 107.170.192.0/18 128.199.0.0/20 128.199.128.0/18 128.199.16.0/20 128.199.192.0/18 128.199.32.0/19 128.199.64.0/18 134.122.0.0/20 134.122.112.0/20 134.122.16.0/20 134.122.32.0/20 134.122.48.0/20 134.122.64.0/20 134.122.80.0/20 134.122.96.0/20 134.209.0.0/20 134.209.112.0/20 134.209.128.0/22 134.209.132.0/22 134.209.136.0/22 134.209.140.0/22 134.209.144.0/20 134.209.160.0/20 134.209.16.0/20 134.209.176.0/20 134.209.192.0/20 134.209.208.0/20 134.209.224.0/20 134.209.240.0/20 134.209.32.0/20 134.209.48.0/20 134.209.64.0/20 134.209.80.0/20 134.209.96.0/20 137.184.0.0/20 137.184.112.0/20 137.184.128.0/20 137.184.144.0/20 137.184.160.0/20 137.184.16.0/20 137.184.176.0/20 137.184.192.0/20 137.184.208.0/20 137.184.224.0/20 137.184.240.0/22 137.184.244.0/22 137.184.248.0/22 137.184.252.0/24 137.184.254.0/24 137.184.255.0/24 137.184.32.0/20 137.184.48.0/20 137.184.64.0/20 137.184.80.0/20 137.184.96.0/20 138.197.0.0/20 138.197.112.0/20 138.197.128.0/20 138.197.144.0/20 138.197.160.0/20 138.197.16.0/20 138.197.176.0/20 138.197.192.0/20 138.197.208.0/20 138.197.224.0/22