[what]
email notification reached to recipient but wrong content in subject and body due to environment variables(like $JOB_NAME, $BUILD_NUMBER) used in subject or in body but not expanded to actual value.
this issue when build failed due to below thrown Jenkins master-slave connection :

stacktrace below:
FATAL: java.io.IOException: Unexpected termination of the channel
hudson.remoting.RequestAbortedException: java.io.IOException: Unexpected termination of the channel
at hudson.remoting.Request.abort(Request.java:295)
at hudson.remoting.Channel.terminate(Channel.java:814)
at hudson.remoting.SynchronousCommandTransport$ReaderThread.run(SynchronousCommandTransport.java:69)
at ......remote call to jptolx22585(Native Method)
at hudson.remoting.Channel.attachCallSiteStackTrace(Channel.java:1356)
at hudson.remoting.Request.call(Request.java:171)
at hudson.remoting.Channel.call(Channel.java:751)
at hudson.remoting.RemoteInvocationHandler.invoke(RemoteInvocationHandler.java:173)
at com.sun.proxy.$Proxy50.join(Unknown Source)
at hudson.Launcher$RemoteLauncher$ProcImpl.join(Launcher.java:979)
at hudson.tasks.CommandInterpreter.join(CommandInterpreter.java:137)
at hudson.tasks.CommandInterpreter.perform(CommandInterpreter.java:97)
at hudson.tasks.CommandInterpreter.perform(CommandInterpreter.java:66)
at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:770)
at hudson.model.Build$BuildExecution.build(Build.java:199)
at hudson.model.Build$BuildExecution.doRun(Build.java:160)
at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:533)
at hudson.model.Run.execute(Run.java:1745)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
at hudson.model.ResourceController.execute(ResourceController.java:89)
at hudson.model.Executor.run(Executor.java:240)
Caused by: java.io.IOException: Unexpected termination of the channel
at hudson.remoting.SynchronousCommandTransport$ReaderThread.run(SynchronousCommandTransport.java:50)
Caused by: java.io.EOFException
at java.io.ObjectInputStream$PeekInputStream.readFully(ObjectInputStream.java:2325)
at java.io.ObjectInputStream$BlockDataInputStream.readShort(ObjectInputStream.java:2794)
at java.io.ObjectInputStream.readStreamHeader(ObjectInputStream.java:801)
at java.io.ObjectInputStream.<init>(ObjectInputStream.java:299)
at hudson.remoting.ObjectInputStreamEx.<init>(ObjectInputStreamEx.java:40)
at hudson.remoting.AbstractSynchronousByteArrayCommandTransport.read(AbstractSynchronousByteArrayCommandTransport.java:34)
at hudson.remoting.SynchronousCommandTransport$ReaderThread.run(SynchronousCommandTransport.java:48)