The Most Valuable Letter You Can Write. © 2002 Jeffrey Dobkin Simple: it’s a thank-you letter. The first reason a thank-you letter is so valuable is obvious - it makes the recipient feel good. This elevates you from the silent majority who never expressed their appreciation in a letter. A phone call just doesn’t have the impact of a letter. In a day, whatever you said on the phone fades into the horizon like the sun. But not a letter. A letter has time to sink in. It can also sit on the rec.