How did marketer locate my email (i.e., the owner's email)?

I made my first site with softr. I published with a custom domain. An ad agency sent me an email soliciting services. The whois data does not expose my email address.

The domain is

same here… I get up to three emails a week…

Do you have an automation that sends emails after form submissions ?

I do

No, I have not implemented anything that would send e-mails.