Supporting Messaging Clients

Require 128-Bit Encryption

The key pairs you configure for TLS encryption consist of a number of bits that indicate the key's security level. You can strengthen security by increasing the encryption level from 40 bits (the default) to 128 bits. The greater the number of bits, the more difficult the item is to decrypt.

Important   Users attempting to access this virtual server must use the same encryption level that you set, or messages will be returned with a non-delivery receipt (NDR).

Note   Due to export restrictions, the 128-bit key strength encryption feature may not be available in all countries. For information about upgrading to 128-bit encryption capability, see

To require 128-bit encryption levels for the virtual server:

  1. Start System Manager
    On the Start menu, point to Programs, point to Microsoft Exchange, and then click System Manager.
  2. Navigate to the SMTP virtual server.
    1. Servers
    2. Server
    3. Protocols
    4. SMTP
    5. SMTP virtual servers
    6. SMTP virtual server
  3. Right-click the SMTP virtual server, and then click Properties.
  4. On the Access tab, under Secure communication, click Communication.
  5. In Security, select the Require secure channel check box if it is not already selected.
  6. Select the Require 128-bit encryption check box.