Unsolicited commercial email (UCE) is just what it sounds like: an email message that you receive without asking for it advertising a product or service. This is also called junk email.
Unsolicited bulk email (UBE) refers to email messages that are sent in bulk to many recipients. UBE may be commercial in nature, in which case it is also UCE. But it may be sent for other purposes as well, such as political lobbying or harassment.
Make money fast (MMF) messages, often in the form of chain letters or multi-level marketing schemes, are messages that suggest you can get rich by sending money to the top name on a list, removing that name, adding your name to the bottom of the list, and forwarding the message to other people. Some also advocate reposting the message to hundreds of newsgroups. MMF messages are considered lotteries in the United States and are illegal. They're also extremely common.
Reputation attacks are messages that appear to be sent from one person or organization, but are actually sent from another. The purpose of the messages isn't to advertise a particular service or product, but to make the recipients of the message angry at the apparent sender. The most nasty reputation attacks include the actual email addresses, phone numbers, and street addresses of the victim or victims. Reputation attacks constitute wire fraud, since they use forged addresses, and are illegal.
One more step in the right direction
Report suspicious messages to the U.S. Federal Trade Commission.
You can also help stop spammers by sending a copy of unlawful messages to the Federal Trade Commission at firstname.lastname@example.org or file a complaint with the FTC.