The first tier ($4/month) only works for up to 25 aliases. Depending on how many of your aliases have leaked, you may have to pay a lot to perform that check.

I wish HIBP had a solution for those of us who are individuals but use domain catchall forwarding as our method for separating accounts.

It feels good to see adobe@mydomain.com, newrelic@mydomain.com, internetarchive@mydomain.com, etc. there but not any of the addresses I use for normal communication.