According to CAN-SPAM legislation, e-mail must meet five basic requirements to avoid being labeled "unsolicited commercial" e-mail:
- The e-mail message must have correct header information.
- The message must have an accurate subject line.
- The message must contain a functioning return e-mail address.
- Senders must not send e-mail more than 10 business days after receiving a request to be removed from a mailing list.
- Commercial e-mail must contain a clear identification that the message is an advertisement, must contain a conspicuous notice of opportunity to decline further e-mail and must display the physical postal address of the sender.