Ask HN: How do I report spam?

Here's the background: I am a Hilton Honors member and as a result, Hilton has my email address. About 2-3mos ago I started noticing a lot of promotional emails (mostly "deals" - e.g., $79 at hotel x, etc.). They seemed to be coming fairly frequently, so I "unsubscribed". This did not appear to have any effect as the emails continued to flow. I then unsubscribed again, but this time I took a screenshot of the confirmation page shown after doing so. I'm now still getting these emails (it's been about 2 weeks since I took the screenshots), so I'm wondering if there is something I can do to report them? My most recent email from them was about "win a grammy weekend in LA". Any suggestions?