wrap ConcurrentDictionary in BlockingCollection

ConcurrentDictionary<int, BlockingCollection<string>> mailBoxes = new ConcurrentDictionary<int, BlockingCollection<string>>();
        int maxBoxes = ;

        CancellationTokenSource cancelationTokenSource = new CancellationTokenSource();
        CancellationToken cancelationToken = cancelationTokenSource.Token;

        Random rnd = new Random();
        // Producer
        Task.Factory.StartNew(() =>
        {
            while (true)
            {
                int index = rnd.Next(, maxBoxes);
                // put the letter in the mailbox 'index'
                var box = mailBoxes.GetOrAdd(index, new BlockingCollection<string>());
                box.Add("some message " + index, cancelationToken);
                Console.WriteLine("Produced a letter to put in box " + index);

                // Wait simulating a heavy production item.
                Thread.Sleep();
            }
        });

        // Consumer 1
        Task.Factory.StartNew(() =>
        {
            while (true)
            {
                int index = rnd.Next(, maxBoxes);
                // get the letter in the mailbox 'index'
                var box = mailBoxes.GetOrAdd(index, new BlockingCollection<string>());
                var message = box.Take(cancelationToken);
                Console.WriteLine("Consumed 1: " + message);

                // consume a item cost less than produce it:
                Thread.Sleep();
            }
        });

        // Consumer 2
        Task.Factory.StartNew(() =>
        {
            while (true)
            {
                int index = rnd.Next(, maxBoxes);
                // get the letter in the mailbox 'index'
                var box = mailBoxes.GetOrAdd(index, new BlockingCollection<string>());
                var message = box.Take(cancelationToken);
                Console.WriteLine("Consumed 2: " + message);

                // consume a item cost less than produce it:
                Thread.Sleep();
            }
        });

        Console.ReadLine();
        cancelationTokenSource.Cancel();