The e-mail client Outlook is an important part of the Exchange system. For the overall security of the system, it is important that Outlook clients be properly configured. The communication protocol selected may already entail specific security issues. Private keys that are used to encrypt and sign e-mails may also be compromised. If network-level encryption is used (based on IPSec or TLS, for example), the encryption mechanism may become ineffective due to an incorrectly configured client. Incorrect configurations may cause security issues such as a loss of confidentiality due to unauthorised access.