Are there any legal issues with direct mail marketing?

[Avrohom New]

Hello fellow Investors,

I recently got a call back from a direct marketing campaign. The person on the other end exclaimed that it was illegal to send mail with an offer to buy an unlisted property! 

I have never heard of any legal issues associated with direct mail marketing, but just in case, would like to hear from fellow members. Has anyone got a response like that before? Are there indeed any legal issues?