1. A system for processing an e-mail, the system comprising: a host, for issuing a first request to get a mail subject of the e-mail; a first sewer, coupled to the host, for sending a first information associated with the e-mail in response to a specific request associated with the first request, wherein the first information includes at least the mail subject and does not include all mail contents of the requested e-mail; a second server, coupled to the host, for analyzing a second information to determine whether or not the mail subject is allowed to be delivered to the host and then outputting an analysis result; and a gateway, coupled to the host, the first sewer, and the second server, for intercepting the first request from the host and generating the specific request to the first server, receiving the first information from the first server and generating the second information according to the received first information, outputting the second information to the second server, receiving the analysis result from the second server, and directing the mail subject to the host if the analysis result indicates the gateway should deliver the mail subject to the host.