Translation of "Inquiry" in Japanese

This subject is outside the scope of our inquiry.

この問題は我々の調査の範囲外である。

He wrote a letter of inquiry to his business contact.

彼は取引先に照会状を書いた。

We have just received an inquiry from Kansas concerning your brother.

ご兄弟のことはカンザス州から問い合わせを受けたばかりです。

Thank you very much if the shipment has already been made and please disregard this inquiry.

出荷済みでしたら、お礼を申し上げるとともに、この依頼を無視してくださるようお願いします。