I saw that a bunch of spam was being attempted from Digital Ocean IP 128.199.173.75, which is a mail server using the domain bpm-ph[.]com. I made an abuse complaint to Digital Ocean, but also thought I'd make one to the domain registrar, which is 101domain[.]com, which has an abuse reporting page. The abuse reporting page seems designed to prevent abuse complaints from getting through -- first, it won't allow text files as evidence attachments, which was easily bypassed by just renaming the text file to a doc file. Second, though, it asks for a contact email address, but it then turns the entire complaint into an email and sends it from the webserver, where it promptly bounces back to the sender if the contact domain is responsibly using DMARC. If you try emailing their abuse address directly, that produces an auto-response that tells you to use the web form. My solution was to use their abuse address as my contact address. It may get bounced, but at least the bounce will go to the right place.