A more thorough explanation:

Definition: UCE is an abbreviation for Unsolicited Commercial Email, also known as spam. It refers to emails that are sent to people without their permission, usually for advertising purposes.

For example, if you receive an email from a company that you have never heard of, promoting their products or services, and you did not sign up to receive emails from them, it is likely UCE or spam.

Many states have laws that prohibit advertisers from sending UCE or spam, and in 2004, the CAN-SPAM Act of 2003 became a federal law in the United States. This law requires that commercial emails include an opt-out option for recipients and prohibits false or misleading information in the email's subject line or content.