process_mailboxes.erl

X = fun() -> 
            lists:foldl(fun(Pid, Acc) ->
                                case erlang:process_info(Pid,message_queue_len) of
                                    undefined ->
                                        Acc;
                                    {_, Len} ->
                                        if
                                            Len > 3 ->
                                                [{Len, process_info(Pid)} | Acc];
                                            true ->
                                                Acc
                                        end
                                end
                        end, [], processes())
    end.