employees of companies with whom you’ve registered that email id sell it for some quick cash on the side.

i can aver this confidently since i know someone from dominos pizza has leaked my email id. i have a convoluted gmail id which i use to register to all these services and – because it’s gmail – i can set up random dots and a custom phrase behind a + to register specific variants to specific companies (e.g., abcxyz123@gmail vs. ab.c.xyz123+dominos@gmail).

all the spam and pseudo-phishing email is sent only to the variant which i’ve registered to dominos and not to a different variant (e.g., a.bcxyz123+bankname@gmail) registered to any other company.

the leaked email id doesn’t contain a name and is too random for it to just be “guessed” by the spammers.