Sự hỗ trợ khách hàng S / MIME chữ ký kiểm tra hộp cho phép các khách hàng để trao đổi các tập tin đính kèm được mã hóa MIME đảm bảo an ninh. E-Mail Domain nút cho phép chúng ta xác định các lĩnh vực e-mail mà chúng tôi sử dụng mã hóa file đính kèm. | 336 Chapter 9 Microsoft Exchange Server Figure The Internet Mail Service. Figure Internet Mail Service tab. Microsoft Exchange Server Chapter 9 337 The Clients support S MIME signatures check box allows clients to exchange encrypted MIME attachments to ensure security. The E-Mail Domain button allows us to specify the e-mail domains in which we use attachment encoding. This means that if we have more than one mail domain we can choose MIME encoding for one and UUENCODE for another. The Connections tab see Figure is another place that we should look to configure the IMS properties. Connections from other servers can be secured on this tab. We can specify that hosts connecting to the server must use authentication and encryption. We can also specify whether the hosts are relay hosts that are used to get e-mail to our server. One of the better -known spamming techniques involves using relay hosts to trick e-mail servers into accepting unsolicited e-mail. Through the Specify by Host button we can accept or block e-mail from specific hosts that are known relay hosts thereby stopping spam from that avenue. Figure shows the Specify by Host option screen where we enter the TCP IP address of the host that we wish to block. We can also block e-mail from specific e-mail addresses and even entire domains by using the Message Filtering button shown in Figure . Figure IMS Connections tab. 338 Chapter 9 Microsoft Exchange Server Figure Specify Hosts to block e-mail delivery. Figure Message Filter blocks mail from specific domains and users. .