The CAN-SPAM Act, is a law that sets the rules for commercial email, establishes requirements for commercial messages, gives recipients the right to have you stop emailing them, and spells out tough penalties for violations.
Among other things, the CAN-SPAM Act requires that:
Your message must include your valid physical postal address. This can be your current street address, a post office box you’ve registered with the U.S. Postal Service, or a private mailbox you’ve registered with a commercial mail receiving agency established under Postal Service regulations.
Your “From,” “To,” “Reply-To,” and routing information – including the originating domain name and email address – must be accurate and identify the person or business who initiated the message.
For these reasons, you should be sure to configure the following in your Comment Mail installation.
See: WordPress Dashboard → Comment Mail → Config. Options → Postmaster / Contact Info