由于地址字迹不清，致使信件无法投递。

It is impossible to deliver this letter because the address is illegible.

《新英汉大辞典》

若无法投递，请退还寄信人。

If undelivered, please return to sender.

youdao

（ 邮件用语） 无法投递时，退回原处。

In case of non - delivery, return to ( the ) sender .

youdao

投递员无法到达我们的林中小屋。

The messenger wasn't able to get through to our cabin in the woods.

youdao

投递员无法到达我们的林中小屋。

The messenger wasn't able to get through to our cabin in the woods.

youdao