Look at the successes, if they have successes from a certain agency, write there.

IF THE ACTORS SIGN THROUGH THE PRODUCTION OFFICE, they won't toss your mail, they'll old on to it. But if the celebrities don't sign through their, then who knows what happens.

I'm not sure if they are still filming, I hope so!
I read on here that Chace Crawford (Nate) signs TTM, they forward the letters he receives through the Gossip Girl address to his office in California

Hello!
I love Gossip Girl and I seeing the fourth season on the italian channel Italia1.
So, I would to write a LOR to Blair (Leighton Meester), Serena (Blake Lively) and Chuck (Ed Westwick).
But I have a doubt: now the actors doesn't filming, so if I send my envelopes to the Gossip Girl Production Office, they throw it or I have any possibilities of answer?
And, if the PO throw my letters, can I write to the Ed agency in United Kingdom? And Blake & Leighton have an agency in any part of the world?
Thank you very much.