Great for neighbors who are friends or acquaintances, this goodbye letter is friendly and polite.
Dear {Recipient},
I heard through the grapevine that you're going to be moving to {place}. We just wanted to thank you for being such great neighbors during your time here and let you know that you will be missed.
Your family has been a great addition to the neighborhood, especially since you {threw BBQs, helped with repairs, etc.} We would love to have you over for dinner before the big move and hear about all of your travel plans. Give us a call sometime this week and we'll set up a time.
Sincerely,
{Sender}