未保存配置更改。
我们应该在publisher.setPresendScript(preSendScript)之后使用job.save()。
工作脚本应为：

for(job in Hudson.instance.items) {
    def list = job.getPublishersList()
    for (publisher in list) {
        if (publisher instanceof hudson.plugins.emailext.ExtendedEmailPublisher) {
            def preSendScript = "your script here"
            publisher.setPresendScript(preSendScript)
        }
    }
    // must have
    job.save()
}