add whenBackToNormalMail.groovy example

declarative-examples/simple-examples/whenBackToNormalMail.groovy

@@ -0,0 +1,37 @@
+pipeline {
+  /*
+   * This example shows how you can send "back to normal" mails.
+   * The post section checks if the build was failed (failure).
+   * If the build was failed an email is sent.
+   * If the build was successfull AND the previous build was failed,
+   * a "back to normal" mail is sent.
+   */
+
+  agent any
+
+  stages {
+    stage("Hello") {
+      steps {
+        sh 'echo "Hello"'
+      }
+    }
+  }
+
+  post {
+    failure {
+      mail to: '[email protected]',
+      subject: "Failed Pipeline: ${currentBuild.fullDisplayName}",
+      body: "Build failed: ${env.BUILD_URL}"
+    }
+
+    success {
+      script {
+        if (currentBuild.previousBuild != null && currentBuild.previousBuild.result != 'SUCCESS') {
+          mail to: '[email protected]',
+          subject: "Pipeline Success: ${currentBuild.fullDisplayName}",
+          body: "Build is back to normal (success): ${env.BUILD_URL}" 
+        }
+      }           
+    }
+  }
+}