Best websites to find correct address and phone for direct mail

[Darina Pogodina]

Hello,

So I started my first mailing campaign. I have letters from one target and post cards for another just to check out both options. What should I do when the card or a letter is sent back to me? What would be the best website or source to find out where the owner is, may be call and make sure my message gets to the owner of the property 100%?

Thank you kindly, 

Darina