I found the solution by research within an older post: JBoss 7.1.3, custom login module and JMS
"for use JMS client with custom login module need add to initial context params:
params.put("jboss.naming.client.connect.options.org.xnio.Options.SASL_POLICY_NOPLAINTEXT", "false"); <-- for allow plain text password from client to server"
Set this property to the InitialContext doing the lookup.
Dont't mess it up with remote.connection.xxxx.connect.options.org.xnio.Options.SASL_POLICY_NOPLAINTEXT=false, which is also necessary for the ejb client lookups!
Maybe this should be explained clearer int Wildfly documentation, because at first glance, it is easy to overlook the diefferent prefixes (remote.connection vs. jboss.naming.client)
Thank you, it worked for me.