I have about 2000 users of my first product. When they bought (over the past 3 years), I didn't have any checkbox on my order page asking if they wanted to receive notifications or updates from my business. I now find myself shipping product number 2, and want to tell my users of product 1 about it, and offer them a discount on the sale price.
My question: Is it legal for me to email them about product number 2 in the absence of explicit permission to email them. Or is my customer contact list now worthless to me?
Update: Just thought I'd give an update. I took the advice given and emailed all 2000 users, with the appropriate 'unsubscribe' links and full contact info. Response was great: no one complained about receiving the email, new website's been busy for 2 days, and sales have been coming in as a result. Very positive result.