Email.

That's right, that thing you check fifty times a day. Its a powerful tool you use every day to communicate with your customers, suppliers and distributors. At the same time, you wade through thousands of solicitations for your money to purchase pharmaceuticals ranging from hair growth to, well... you've already had the misfortune of reading them once. Let's not do it again.

But that is not why its your friend or enemy. We are talking about something different here.