A week ago I've started getting some weird behavior of notification delivery plugins. I'm able to send a test message from jenkins to my gmail account. However, when any job is executed, no notification is ever delivered. Logs seem uninformative as well as build output. I've attached relevant screen shots.

Note:
I've upgraded to the latest LTS version and have updated all of the plugins.

Build output excerpt:
_Email was triggered for: Always
Sending email for trigger: Always
Sending email to: myaccount@gmail.com
Finished: SUCCESS_

Log excerpt:
Apr 05, 2016 11:43:34 AM WARNING hudson.ExtensionFinder$Sezpoz scout
Failed to scout com.cloudbees.hudson.plugins.folder.properties.AuthorizationMatrixProperty$DescriptorImpl
java.lang.InstantiationException: java.lang.NoClassDefFoundError: com/cloudbees/hudson/plugins/folder/AbstractFolderPropertyDescriptor
at net.java.sezpoz.IndexItem.element(IndexItem.java:146)
at hudson.ExtensionFinder$Sezpoz.scout(ExtensionFinder.java:666)
at hudson.ClassicPluginStrategy.findComponents(ClassicPluginStrategy.java:382)
at hudson.ExtensionList.load(ExtensionList.java:349)
at hudson.ExtensionList.ensureLoaded(ExtensionList.java:287)
at hudson.ExtensionList.iterator(ExtensionList.java:156)
at hudson.ClassicPluginStrategy.findComponents(ClassicPluginStrategy.java:381)
at hudson.ExtensionList.load(ExtensionList.java:349)
at hudson.ExtensionList.ensureLoaded(ExtensionList.java:287)
at hudson.ExtensionList.iterator(ExtensionList.java:156)
at jenkins.model.Jenkins.getDescriptorByType(Jenkins.java:1231)
at hudson.plugins.copyartifact.BuildSelectorParameter.initAliases(BuildSelectorParameter.java:152)
at hudson.plugins.copyartifact.CopyArtifactPlugin.postInitialize(CopyArtifactPlugin.java:35)
at hudson.PluginManager$2$1$2.run(PluginManager.java:403)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:169)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:282)
at jenkins.model.Jenkins$8.runTask(Jenkins.java:924)
at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:210)
at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:117)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NoClassDefFoundError: com/cloudbees/hudson/plugins/folder/AbstractFolderPropertyDescriptor
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at jenkins.util.AntClassLoader.defineClassFromData(AntClassLoader.java:1139)
at hudson.ClassicPluginStrategy$AntClassLoader2.defineClassFromData(ClassicPluginStrategy.java:801)
at jenkins.util.AntClassLoader.getClassFromStream(AntClassLoader.java:1310)
at jenkins.util.AntClassLoader.findClassInComponents(AntClassLoader.java:1366)
at jenkins.util.AntClassLoader.findClass(AntClassLoader.java:1326)
at sun.reflect.GeneratedMethodAccessor5.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at jenkins.ClassLoaderReflectionToolkit.invoke(ClassLoaderReflectionToolkit.java:44)
at jenkins.ClassLoaderReflectionToolkit._findClass(ClassLoaderReflectionToolkit.java:86)
at hudson.PluginManager$UberClassLoader.findClass(PluginManager.java:1188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
at net.java.sezpoz.IndexItem.element(IndexItem.java:134)
... 21 more
Caused by: java.lang.ClassNotFoundException: com.cloudbees.hudson.plugins.folder.AbstractFolderPropertyDescriptor
at jenkins.util.AntClassLoader.findClassInComponents(AntClassLoader.java:1376)
at jenkins.util.AntClassLoader.findClass(AntClassLoader.java:1326)
at jenkins.util.AntClassLoader.loadClass(AntClassLoader.java:1079)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
... 37 more

Apr 05, 2016 11:43:36 AM WARNING hudson.ExtensionFinder$Sezpoz _find
Failed to load com.cloudbees.hudson.plugins.folder.properties.AuthorizationMatrixProperty$DescriptorImpl
java.lang.InstantiationException: java.lang.NoClassDefFoundError: com/cloudbees/hudson/plugins/folder/AbstractFolderPropertyDescriptor
at net.java.sezpoz.IndexItem.element(IndexItem.java:146)
at hudson.ExtensionFinder$Sezpoz._find(ExtensionFinder.java:628)
at hudson.ExtensionFinder$Sezpoz.find(ExtensionFinder.java:617)
at hudson.ExtensionFinder$GuiceFinder.<init>(ExtensionFinder.java:256)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at java.lang.Class.newInstance(Class.java:383)
at net.java.sezpoz.IndexItem.instance(IndexItem.java:181)
at hudson.ExtensionFinder$Sezpoz._find(ExtensionFinder.java:642)
at hudson.ExtensionFinder$Sezpoz.find(ExtensionFinder.java:617)
at hudson.ClassicPluginStrategy.findComponents(ClassicPluginStrategy.java:388)
at hudson.ExtensionList.load(ExtensionList.java:349)
at hudson.ExtensionList.ensureLoaded(ExtensionList.java:287)
at hudson.ExtensionList.iterator(ExtensionList.java:156)
at hudson.ClassicPluginStrategy.findComponents(ClassicPluginStrategy.java:381)
at hudson.ExtensionList.load(ExtensionList.java:349)
at hudson.ExtensionList.ensureLoaded(ExtensionList.java:287)
at hudson.ExtensionList.iterator(ExtensionList.java:156)
at jenkins.model.Jenkins.getDescriptorByType(Jenkins.java:1231)
at hudson.plugins.copyartifact.BuildSelectorParameter.initAliases(BuildSelectorParameter.java:152)
at hudson.plugins.copyartifact.CopyArtifactPlugin.postInitialize(CopyArtifactPlugin.java:35)
at hudson.PluginManager$2$1$2.run(PluginManager.java:403)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:169)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:282)
at jenkins.model.Jenkins$8.runTask(Jenkins.java:924)
at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:210)
at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:117)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NoClassDefFoundError: com/cloudbees/hudson/plugins/folder/AbstractFolderPropertyDescriptor
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at jenkins.util.AntClassLoader.defineClassFromData(AntClassLoader.java:1139)
at hudson.ClassicPluginStrategy$AntClassLoader2.defineClassFromData(ClassicPluginStrategy.java:801)
at jenkins.util.AntClassLoader.getClassFromStream(AntClassLoader.java:1310)
at jenkins.util.AntClassLoader.findClassInComponents(AntClassLoader.java:1366)
at jenkins.util.AntClassLoader.findClass(AntClassLoader.java:1326)
at sun.reflect.GeneratedMethodAccessor5.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at jenkins.ClassLoaderReflectionToolkit.invoke(ClassLoaderReflectionToolkit.java:44)
at jenkins.ClassLoaderReflectionToolkit._findClass(ClassLoaderReflectionToolkit.java:86)
at hudson.PluginManager$UberClassLoader.findClass(PluginManager.java:1188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
at net.java.sezpoz.IndexItem.element(IndexItem.java:134)
... 31 more
Caused by: java.lang.ClassNotFoundException: com.cloudbees.hudson.plugins.folder.AbstractFolderPropertyDescriptor
at jenkins.util.AntClassLoader.findClassInComponents(AntClassLoader.java:1376)
at jenkins.util.AntClassLoader.findClass(AntClassLoader.java:1326)
at jenkins.util.AntClassLoader.loadClass(AntClassLoader.java:1079)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
... 47 more
...
Apr 05, 2016 1:35:33 PM WARNING javax.jmdns.impl.DNSIncoming readAnswer
There was an OPT answer. Not currently handled. Option code: 65002 data: 1DC0C283F3512719
Apr 05, 2016 1:35:42 PM WARNING javax.jmdns.impl.DNSIncoming readAnswer
There was an OPT answer. Not currently handled. Option code: 65002 data: 1DC0C283F3512719