Jenkins build Failed but all stages Succeeded

As the send email step is failing, can you try using:

environment {            EMAIL_TO = 'someone@host.com'        }    post {            failure {                emailext body: 'Check console output at $BUILD_URL to view the results. \n\n ${CHANGES} \n\n -------------------------------------------------- \n${BUILD_LOG, maxLines=100, escapeHtml=false}',                         to: EMAIL_TO,                         subject: 'Build failed in Jenkins: $PROJECT_NAME - #$BUILD_NUMBER'            }        }

You need to check the Console log of that job, though all the stages Succeded, there must be a step that is failing at last part.

If you want to send an e-mail to the right developer, you can try something like this :

pipeline {    agent any     stages {        stage('A') {            steps {                ...            }        }        stage('Test') {            steps {                ...            }        }    }    post {         always {                emailext  body: "${currentBuild.currentResult}: Job ${env.JOB_NAME} build ${env.BUILD_NUMBER}\n More info at: ${env.BUILD_URL}",                recipientProviders: [[$class: 'DevelopersRecipientProvider'], [$class: 'RequesterRecipientProvider']],                subject: "[Jenkins] Build ${currentBuild.currentResult}: Job ${env.JOB_NAME}"        }    }}