"手が空いたら返信ください"
- Please answer when you are able.
- Please reply when you have the time.
「お忙しいところ申し訳ないですが、手が空いたら返信ください」
- I’m sorry to bother you but please give me a reply when you are able.
- I’m sorry for bothering you duringa busy time, but please answer when you have the time.