Even if they haven't bought from you in years, a former business relationship is a good reason to re-introduce yourself.
1234, Main Street
Boston, MA 02123
08 April, 2005
<Recipient Address Goes Here>
It's been quite awhile since we've had the opportunity to serve you. However, I thought you might be interested in what has been happening with Abc Company since then. <Bring customer up to date on changes.>
<Details of changes and benefits.>
I'd like to request some of your time to find our how you're doing and if there is anything we might help you with. I'll call you <time> to see when we might be able to meet. In the meantime, if you have any questions, you may reach me at <phone number>. We look forward to doing business with you again.
encl: <List of enclosed items goes here>