CAN-SPAM (Controlling the Assault of Non-Solicited Pornography And Marketing) is an act that was passed in 2003. That act formulates the rules for commercial email and commercial messages. It gives recipients the right to have a business stop emailing them and also outlines the penalties incurred for those who violate the law.
CAN-SPAN law covers 'any electronic mail message the primary purpose of which is the commercial advertisement or promotion of a commercial product or service' including email that promotes content on commercial websites. The law makes no exception for business-to-business email. It does, however, exempt transactional and relationship messages.
Penalties for non-compliance
For every single email that violates the CAN-SPAM Act, the FTC will fine you $16,000. So if you have sent 10000 emails then you are liable to penalties upto 160,000,000$ which is 160 million $
Do's and Don't for CAN-SPAM compliance
For CAN-SPAM compliance you need to have the following in every email that you send out:
Your valid physical postal address
Provide clear way to unsubscribe to your emails and honour unsubscribe within 10 business days
Clear From, To and Reply-To which explains clearly who you are
For more detailed understanding of the act kindly refer here