This letter can be used as a follow-up to a customer after a sale.
{Date}
To: {Name}
{Address}
{City, State, Zip}
Dear {Recipient},
I just wanted to write to thank you again for {details of the sale}.
I was happy to be able to provide you with {what was provided in the sale} and I look forward to our continued relationship.
Remember that {name of company} will always be here to provide you with {what you provide customers} and, of course, excellent customer service. If there is anything more I can help you with, please don't hesitate to call.
Thank you,
{Sender}