I had a success from her last year using this address:

Olivia Newton-John
PO Box 585
Oak Lawn, IL 60454

I wrote her July 2004 and received my photos back signed October 2005.

I received his autograph through the mail back when he first joined OLTL, using the OLTL studio address. Hope that helps.

Has anyone had any successes using the address on fanmail.biz? He's the actor who played Young Indiana Jones and I've always wanted his autograph. Thanks!