Can we mail to the people who previously “unsubscribed” since this new mailing will have a different focus?

Definitely not based on the Federal Trade Commission's definition of the CAN-SPAM Act of 2003. Here's what the law ( http://www.ftc.gov/bcp/conline/pubs/buspubs/canspam.htm ) says: When you receive an opt-out request, the law gives you 10 business days to stop sending email to the requestor's email address. You cannot help another entity send email to that address, or have another entity send email on your behalf to that address. Finally, it's illegal for you to sell or transfer the email addresses of people who choose not to receive your email, even in the form of a mailing list." Each violation of the above provisions is subject to fines of up to $11,000.