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.
If I recall, the founder had some workaround for situations like you describe. I am in the same situation but I didn’t have the effort to care enough to do all that hassle.
It’s entirely possible that my best fix is just to delete my haveibeenpwned account and react when I get spam, but where’s the fun in that?
The founder was asked to provide a subscription level for individual domains and he said no and pointed people at the suggestion to search manually or occasionally pay for a month instead.