A letter allows you to be more personal with customers. Letters work in different ways.
If you know how to write letters of apology that sound really sincere, you can turn irate customers into ones who will gladly do future business with you.
Search through your database and look for names of previous customers who have already stopped buying from you. Compose letters to tell them how much you want them back.
There are at least two reasons why building alliances with other companies can be beneficial.
You can have access to a bigger audience. With resources and skills combined, a joint venture means you can have more exposure and opportunities to gain bigger profits.