Nodemailer发送邮件频繁ETIMEDOUT：偶发成功但超时问题求助

问题概述 #

邮件仅能偶尔成功发送，多数情况下会卡在“Resolved”状态后触发超时（已设置超时时间），且频繁出现ETIMEDOUT错误。触发方式包括ReactJS站点按钮点击，以及用Thunder Client直接调用API，结果一致。控制台可见邮件最终发送成功但随后超时。

相关代码 #

创建Transporter的函数 #

const createTransporter = (serviceSettings) => {
// Define which service to use
// gmail    = Use gmail's service (must have GmailSMTPUser and GmailSMTPAppPass setup)
// ll       = Use LumiereLabs's service
const emailService = serviceSettings.use
// Configure the transporter

switch (emailService) {
    case "gmail":
        return nodemailer.createTransport({
            service: 'gmail',
            auth: {
                user: serviceSettings.services.gmail.user,
                pass: serviceSettings.services.gmail.pass
            },
            logger: true,
            debug: true,
            maxConnections: 5, // Maximum number of connections to keep in the pool
            maxMessages: 100, // Maximum number of messages to send per connection
            rateLimit: 10, // Maximum number of messages to send per second
            pool: true, // disable connection pooling
            connectionTimeout: 10000,  // 10 seconds
            socketTimeout: 10000,      // 10 seconds
            greetingTimeout: 5000      // 5 seconds    
        })
    break

    case "ll":
        return nodemailer.createTransport({                    
            host: 'smtp.lumierelabs.org',
            port: 587,
            secure: false,       // true for 465, false for others
            requireTLS: true,
            auth: {
                user: serviceSettings.services.ll.user,
                pass: serviceSettings.services.ll.pass
            },
            tls: {
                rejectUnauthorized: false // if using self-signed certificates
            },
            logger: true,
            debug: true,
            maxConnections: 5, // Maximum number of connections to keep in the pool
            maxMessages: 100, // Maximum number of messages to send per connection
            rateLimit: 10, // Maximum number of messages to send per second
            pool: true, // disable connection pooling
            connectionTimeout: 10000,  // 10 seconds
            socketTimeout: 10000,      // 10 seconds
            greetingTimeout: 5000      // 5 seconds                
        })
    break
}

邮件发送处理函数 #

const sendEmail = async (mailOptions, successMessage, res, serviceSettings) => {
let toasts = []

const transporter = createTransporter(serviceSettings)
            
try {
    let info = await transporter.sendMail(mailOptions)

    // Send to notification
    toasts.push({ message: successMessage, object: { sentEmail: true }, type: 'success' })

    // Send to console
    console.log('Email sent: ' + info.response)
} catch (error) {
    // Send to notification
    toasts.push({ message: `Error sending mail: ${error}`, object: { sentEmail: false },  type: 'error'})

    // Send to console
    console.error('Error sending email: ', error)

    // Rethrow error to handle it upstream
    throw error
} finally {
    transporter.close() // close the connection pool

    // return something
    if(toasts.length > 0) {
        // Toasts found!
        // Check for type
        if (toasts[0].type === "error") {                                               
            // Error                                                                        
            if (!res.headersSent) {
                return res.status(400).json(toasts)
            } else {
                console.warn('Attempted to send a response after headers were already sent.');
            }                      
        } if (toasts[0].type === "unauthorized") {
            // Unauthorized
            if (!res.headersSent) {
                return res.status(401).json(toasts)
            } else {
                console.warn('Attempted to send a response after headers were already sent.');
            }                      
        } else {
            if (!res.headersSent) {
                return res.status(200).json(toasts)
            } else {
                console.warn('Attempted to send a response after headers were already sent.');
            }                      
        }
    }
}

该函数在ExpressJS后端的userController.js中通过await sendEmail(mailOptions, successMessage, res, serviceSettings)调用。

环境信息 #

• Node版本：22.2.0
• NPM版本：10.7.0
• 开发系统：Windows 11
• SMTP服务器系统：Ubuntu 22.04（搭载Postfix和Dovecot）

已尝试的排查措施 #

• 从自建SMTP服务器（smtp.lumierelabs.org）切换至Gmail服务，问题依旧，排除SMTP服务器问题
• 搭建独立测试应用仅使用Nodemailer，问题复现
• 重启电脑，无改善
• 通过命令行telnet测试smtp.lumierelabs.org，服务器正常
• 重新安装Nodemailer
• 搜索相关问题未找到类似案例
• 关闭Windows Defender防火墙，无变化

恳请各位提供解决方案或排查思路。

内容的提问来源于stack exchange，提问作者FinuxFirit