Starting with Message Queue 4.0, the default value for the client connection factory property imqSSLIsHostTrusted is false. If your application depends on the prior default value of true, you need to reconfigure and to set the property explicitly to true.
You might choose to trust the host when the broker is configured to use self-signed certificates. In this case, in addition to specifying that the connection should use an SSL-based connection service (using the imqConnectionType property), you should set the imqSSLIsHostTrusted property to true.
For example, to run client applications securely when the broker uses self-signed certificates, use a command like the following.
java -DimqConnectionType=TLS -DimqSSLIsHostTrusted=true ClientAppName
To use the Command utility (imqcmd) securely when the broker uses self-signed certificates, use a command like the following (for listing connector services).
imqcmd list svc -secure -DimqSSLIsHostTrusted=true