Here is the short description An open relay (sometimes called an insecure relay or a third-party relay) is an SMTP e-mail server that allows third-party relay of e-mail messages. By processing mail that is neither for nor from a local user, an open relay makes it possible for an unscrupulous sender to route large volumes of spam. In effect, the owner of the server -- who is typically unaware of the problem -- donates network and computer resources to the sender's purpose. In addition to the financial costs incurred when a spammer hijacks a server, an organization may also suffer system crashes, equipment damage, and loss of business. In the past, open relays were used intentionally, for example, to facilitate mail relay between the separate closed e-mail systems (such as UUCP or FidoNet) or to allow network administrators to debug mail connectivity issues and route mail around known problems. However, the Internet has expanded enormously since then, and the potential for abuse has...