英语书信的写作格式遵循一定的规范，包括信头、称呼、正文、结束语和签名等部分。下面我将根据这些要素，为你生成一篇简短的英文书信示例，字数控制在500字以内。

Dear [Recipient's Name],

I hope this letter finds you well. It has been quite some time since we last met, and I have often found myself reminiscing about the good times we shared during our college days. I trust that you are in good health and high spirits.

As for me, life has been busy but fulfilling. I recently completed my master’s degree in Environmental Science, which has opened up several exciting opportunities for me. I am currently working as a research assistant at a leading environmental organization, where I get to work on projects that aim to tackle climate change and promote sustainable living. It is a challenging yet rewarding role that allows me to contribute positively to society.

I would love to hear more about what you have been up to lately. How is your family? Have you pursued any new hobbies or interests? Do you remember the time when we used to explore the city together? Those were indeed memorable moments.

In closing, I would like to express my gratitude for your friendship. Our friendship has been a source of strength and joy for me, and I cherish every moment we spend together. I look forward to hearing from you soon and hopefully catching up in person sometime in the future.

Warm regards,

[Your Name]

这封信包含了对收件人的问候、自我介绍以及对过去的回忆。同时，也表达了对对方近况的好奇，并邀请对方回复。最后，用温暖的祝愿作为结尾。这样的书信既体现了个人情感，又保持了礼貌与正式。