Skip tracing returned mail

[Michael Kev]

Does anyone here skip trace the owners on returned mail? I've been sending out letters and I've heard it's a good idea to find the owners of a property, especially the vacant ones. I'm thinking of using TLO or another skip trace company, just wanted to get peoples thoughts on what type of returned mail you guys do this for.

Do you only do it for properties returned "vacant" or would you do it for any type (ie - attempted, not known)?