Overview: Yes, people still do write business letters. The business letter, like your other printed pieces, should reflect your brand and the quality of your products.
If you're a smaller business, don't be afraid to write a personalized letter to your customer by laser-copying your letterhead. Word can do the personalization to swap out customer names on each letter. Make sure you include an offer and hand sign each letter. Word can also do the envelope addressing. These letters get opened and people like the personal touch.