I think we can do a process of elimination by accounting all sources you guys used your personal email at and narrowing down to 1-3 possible culprits and make a guess.
Just a thought, why would an established vendor (like Korin or JCK) sell a list of their customers to a competitor, unless it is a subsidiary? It doesn't make sense.
F+W Media (KF)? That's a possibility, but then they are not being very thorough, as I haven't received anything.