I'm too bad with regex, but lets give it a try.
According to mampakhas regex, it will also accept
apple.com

I'm not sure if thats allowed. This is modification to mampakha's regex..check if this one works
^((\*\.|[a-zA-Z0-9]+\.))+([a-zA-Z0-9]+\.)+[a-zA-Z]{2,3}$

oops too late

anyway herez modified of myself since the prev one of mine will also accept  test.*.appale.com
^((\*\.|[a-zA-Z0-9]+\.)){1}([a-zA-Z0-9]+\.)+[a-zA-Z]{2,3}$