There are many types of anonymous mail software. There are anonymous mailers that are designed to be secure against determined attacks, such as the Mixmaster network. There are also anonymous mail systems which are really for fun. These provide weak security guarantees but are often easier to use and more reliable. All these will be found here. Anonymous communication is a two-edged sword. It benefits society by allowing whistleblowers to speak up freely, and by assisting those whose free speech rights are being infringed. It can also be used to conceal the origin of unethical activities such as spam and computer break-ins. Sites which promote these types of activities are not listed here.
More information