Dear Tom,
It's been two months since I last heard from you, and I've been wondering how you are. I hope you aren't ill or in any kind of trouble.
I have to admit that I feel a bit sad about the silence. Every day when I check the post, I hope to see your handwriting on an envelope, and every time I'm disappointed. After so long, I'm starting to worry that I may have said something to upset you, or that you've lost interest in writing.
Your letters have meant so much to me over the past three years. I loved hearing about your family, your city and your adventures, and they often cheered me up on bad days. They also helped my English enormously, and I've kept every single one in a box under my bed.
Please tell me what has happened! Are you very busy at work, or have you moved house? If you simply forgot, that's fine, but please write back soon, even if it's just a few lines. I'd really like us to stay in touch.
I'm looking forward to your reply.
Best wishes,
Mehmet