he has not sent me his address .He does not want me to write

he has not sent me his address .He does not want me to write to him (so that)
连接以上句子,用括号中的词语替代动词want
He has not sent me his address so that I will/shall not be able to write to him.
为什么多了be able to这个短语?
应该是这样呀：
He has not sent me his address so that I will/may not write to him.
答案是不是错了?如果我是错的,请分析一下原因,