My personal domain has hundreds of aliases - one for each site I deal with. This is great for identifying the source of spam, and I retire any aliases that get spam.

haveibeenpwned.com lets me add a domain, but wants 3912 USD a year to actually tell me which addresses leaked. This is obviously an insane price for a nice-to-have.

Is there an alternative for free or very cheap? A self-hosted tool that would pull down lists would be great, but I suppose those lists aren't public.