Creator of pixeldrain here. Italy has been doing this for a very long time. They never notified me of any such material being present on my site. I have a lot of measures in place to prevent the spread of CSAM. I have sent dozens of mails to Polizia Postale and even tried calling them a few times, but they never respond. My mails go unanswered and they just hang up the phone.
Have you tried Europol?
Not yet. I also thought about reaching out to the embassy, but have not had the time for it yet.
As far as I know, Europol can route your report to appropriate local authority.
Thanks, I'll give them a call tomorrow. The website only lists a dutch phone number, which is convenient, I'm dutch as well.
Don't use your ISP's DNS. Switch to something outside of their control.