What is spam?
Spam is unsolicited, unwanted marketing email.
How to opt-out
The federal CAN-SPAM Act requires that a commercial emailer give each email recipient an opt-out method. A commercial emailer must provide a return email address or another Internet-based response mechanism that allows a recipient to ask the emailer not to send future email messages to the recipient’s email address. The law requires that commercial email be identified as an advertisement and include the sender's valid physical postal address. The message must contain a clear and conspicuous notice that the message is an advertisement or solicitation and that the recipient can opt-out of receiving more commercial email. It also must include a valid physical postal address.
The federal spam law doesn’t work very well to deter most spam. However, any legitimate company using email for advertising is likely to comply. If you receive an email from someone you recognize as a legitimate company and it has an opt-out, you can stop that company from emailing you again. This is a very powerful tool because it flatly prohibits more commercial email from that sender to your email address.
To opt-out: First, make sure the email is a CAN-SPAM compliant email. Some emails offer opt-outs, but the opt-outs are fake. A CAN-SPAM compliant email will be labeled as an advertisement, will include a valid postal address for the sender, and will include a workable opt-out link of some type. If all three elements are present, then the opt-out is probably valid; however, you will have to use your own judgment about each email. Transactional emails are not required to offer an opt-out. For example, if you place an online order with an Internet merchant, the message confirming your order, informing you of the shipping date, etc., need not offer an opt-out. However, if you get a message a month later announcing a sale, that commercial email should include an opt-out.
More information about CAN SPAM: FTC CAN SPAM page.