Typically refers to an e-mail server (SMTP server) that is configured to deliver any incoming mail to another mail server. In the past, open relays (open relay servers) were common, but today, most e-mail servers block all e-mail that does not originate with the customers of the service or employees of the company. The term may also apply to a proxy server that can be used by the general public. See spam relay and anonymous remailer.