here is your express mail had been kept here yesterday.

题目

here is your express mail had been kept here yesterday.
here is your express是不是句子主语? 还有这里用had 可不可以?
due to the lack of your detailed address, 这里这个the是什么意思,可以去掉吗?
三个问题

答案

这是你昨天存在这里的快件.
倒装句,主语是 your express mail ,had been kept here yesterday是后置定语.had been kept可用,但建议改成(which was——省略) kept.
the不可去掉,就是定冠词特指,表原因.