Selling support is different from selling products in many ways but one difference is inescapable: it’s hard to sell support for product X to customers who don’t already own product X. In other words, your pool of prospects is limited and defined ahead of time.
So why do we often restrict the pool further, to those customers of product X who already have a support contract? That’s right: most support organizations focus their selling efforts on renewing existing contracts and completely neglect customers who dropped support in the past. That could be a good thing: many customers who drop support do so because they are no longer using the product, so they won’t need support either. But what of customers who dropped support because of budget considerations or a temporary shelving of the product? What about instituting a “get in touch” program to contact customers who were once on a support contract but dropped out? If they are no longer using the product, make a note to leave them alone and move on. If they are using the product, see if you can put together a reasonable “come back to the fold” offer.