How do I add system properties to a Fabric environment?

Issue

• How do I add system properties to a Fabric environment?
• What si the best option for setting system property in Fuse or JBoss A-MQ ?
• Suppose while sending email we need to set the property "java.net.preferIPv4Stack" to "true" before sending the email. We have tried setting this property in the "system.properties" of container, also we have tried setting this property in the "karaf.bat" in "JAVA_OPTS".
• Suggest on how we can set this property and where.