I am glad to receive your letter of May 20th，2018，in which you asked information about“Aiding Rural Primary Schools”project. I am writing this letter to give a replay.
【①I am glad to receive your letter of+具体时间，in which you asked in formation about“...”project.（很高兴收到你......的来信，你在心中询问了“......”项目的信息。）②I am writing this letter to give a replay.我写这封信为了回答你的询问。】
Firstly，with respect to the basic requirements of volunteers，I would like to tell you that there is a chance that can be offered to international students and you are qualified for it. Secondly，since you want to prepare some activities to help students with their spoken English，I have enclosed a list about the detailed arrangement of the project.
【①with respect to ...，I would like to tell you that +从句...（关于......，我想告诉你，......）②since+从句...，+主句...（因为......，所以......）】
I hope that the above information can be helpful. And you could ask me at any time if there is other information you need.
【询问信结尾段：I hope that the above information can be helpful. And you could ask me at any time if there is other information you need.我希望以上信息能对你有所帮助。你也可以随时问我其他你需要的信息。】