Email address verification

verify-email.js

import Dns from 'dns'
import Net from 'net'

class VerifyMail {
  constructor (email) {
    this.email = email
  }

  fetchMx (domain) {
    return new Promise((resolve, reject) => {
      Dns.setServers(['223.5.5.5', '223.6.6.6'])
      Dns.resolveMx(domain, (err, data) => {
        if (err) return reject(err)
        return resolve(data)
      })
    })
  }

  sendMSG1(socket) {
    return new Promise((resolve, reject) => {
      console.log('=> HELO verify-email')
      socket.write('HELO verify-email\r\n', resolve)
    })
  }

  sendMSG2(socket) {
    return new Promise((resolve, reject) => {
      const from = 'verify-email@gmail.com'
      console.log(`=> MAIL FROM: <${from}>`)
      socket.write(`MAIL FROM: <${from}>\r\n`, resolve)
    })
  }
  sendMSG3(socket) {
    return new Promise((resolve, reject) => {
      console.log(`=> RCPT TO: <${this.email}>`)
      socket.write(`RCPT TO: <${this.email}>\r\n`, resolve)
    })
  }

  sendMSG4(socket) {
    return new Promise((resolve, reject) => {
      console.log(`=> QUIT`)
      socket.write(`QUIT\r\n`, resolve)
    })
  }

  verify (email, domain) {
    return new Promise((resolve, reject) => {
      let data = Buffer('')
      const socket = Net.connect(25, domain)
      socket.on('error', err => {
        console.error('err', `* Connection STMP server failed, ${err.message}`)
        return reject(err)
      })
      socket.on('data', (chunk) => {
        console.log(`<= ${chunk.toString('utf8').trim()}`)
        data = Buffer.concat([data, chunk])
      })
      socket.on('connect', async () => {
        console.log(`* Connection succeeded to ${domain} SMTP.`)
        await this.sendMSG1(socket)
        await this.sendMSG2(socket)
        await this.sendMSG3(socket)
        await this.sendMSG4(socket)
      })
      socket.on('end', () => {
        const verify = !data.toString('utf8').includes('550')
        console.log(`\n* ${this.email} - Result: ${verify ? 'Success': 'Bad'}`)
        return resolve(verify)
      })
    })
  }

  async run () {
    const email = this.email
    const domain = email.split('@')[1]
    try {
      const mxList = await this.fetchMx(domain)
      const mx = mxList[0].exchange
      console.log(`* MX record about ${domain} is ${mx}.`)
      return this.verify(email, mx)
    } catch (err) {
      console.log(`* Fetch MX record about ${domain} failed. ${err.message}`)
      throw err
    }
  }
}

const EMAIL = 'admin@qq.com'
console.log(`* Target email: ${EMAIL}`)

const verifyMail = new VerifyMail(EMAIL)
verifyMail.run()

验证原理

MX record found: mx3.qq.com (Priority 10)
MX record found: mx2.qq.com (Priority 20)
MX record found: mx1.qq.com (Priority 30)
Connecting to mx3.qq.com
Connected to mx3.qq.com
Dialog with mx3.qq.com ok
------------------------------------------------------------
220 newusamx25.qq.com MX QQ Mail Server
HELO verifyemailaddress.org
250 newusamx25.qq.com
MAIL FROM: <noreply@verifyemailaddress.org>
250 Ok
RCPT TO: <master@qq.com>
550 Mailbox not found. http://service.mail.qq.com/cgi-bin/help?subtype=1&&id=20022&&no=1000728
QUIT
------------------------------------------------------------
Email address master@qq.com rejected