How can I make sure my email are CAN SPAM compliant ?
Can Spam is an anti-spam law passed in the United States, but applies in theory internationally. It defines what should be contained in an email you send, and to prevent the sending of spam.
The act specifies the main aspects of an email that will prevent it being marked as spam
1. An opt-out (or unsubscribe) option
2. A valid Subject and header information
3. A legitimate sending email from the sender
4. Valid company and contact information in the email
The application gives you the options to comply with this, such as forcing an unsubscribe link and making it easy for this process to be included for your lists.
You can view a Wikipedia entry about the Can-Spam Act here