我为Jenkins（2.176.3）安装了Email Extension Plugin（2.66），以便在Pipelines中使用，我正在尝试以下示例：https://medium.com/@gustavo.guss/jenkins-sending-email-on-post-build-938b236545d2

pipeline {
    environment {
        //This variable need be tested as string
        doError = '1'
    }

    agent any

    stages {
        stage('Error') {
            when {
                expression { doError == '1' }
            }
            steps {
                echo "Failure"
                error "failure test. It's work"
            }
        }

        stage('Success') {
            when {
                expression { doError == '0' }
            }
            steps {
                echo "ok"
            }
        }
    }
    post {
        always {
            echo 'I will always say Hello again!'

            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}"

        }
    }
}

但我有以下错误：
执行始终发布条件时出错：java.lang.NoSuchMethodError:在步骤[版本号，接受GitLabMR，添加GitLabMRComment，存档，bat，构建，捕获错误， checkout ，删除目录，目录，停靠指纹来源，停靠指纹运行，echo，工具的环境变量，错误，文件存在，查找文件，获取上下文，...]中未找到此类DSL方法'电子邮件扩展'
此外，我无法配置插件本身，我不知道如何激活它，我重新启动Jenkins，系统并没有工作，管道语法编辑器不承认插件，任何建议？