If your website doesn't have a sign up form for a newsletter, you are losing very valuable prospect data. When a visitor goes to your website, they are often looking for a product or information that you provide. It makes sense, then, that many of these visitors would be willing to sign up for a newsletter with good quality content and more information on your industry and products.
By starting a monthly email newsletter, you will be able to collect prospect data and be able to stay in touch with your customers and most interested prospects. You'll increase your visitor to sales conversion rate, while at the same time build your reputation in your industry and relationships with your customers and prospects.