Reinforce how important this customer's business is to you before trying to sell additional services or products. Be clear about how this offer is of benefit to him or her.
1234, Main Street
Boston, MA 02123
09 April, 2005
<Recipient Address Goes Here>
We value our customers and are constantly looking for ways to serve them better. We have found that many of our customers <biggest need>. That is why I am writing you today.
We believe that we have a solution. <Explain new service or product.> I'll call you in the next 10 days to discuss your needs. In the meantime, please don't hesitate to call us at <phone number> if you have any questions. It's been a pleasure serving you in the past and we look forward to meeting your needs in the future.
encl: <List of enclosed items goes here>