Why do certain emails go missing when attempting to fetch them using IMAP?

Question

import Imap from 'node-imap'
import { simpleParser } from 'mailparser'
import { inspect } from 'util'

export default async function handler(req, res) {
  try {
    const cred = req.body

    const imap = new Imap({
      user: cred.email,
      password: cred.password,
      host: cred.server,
      port: 993,
      tls: true
    })

    imap.on('ready', async function () {
      try {
        const messages = await fetchMessages(imap)
        res.status(200).json(messages)
      } catch (error) {
        console.error('Error fetching messages:', error)
        res.status(500).json({ error: 'An error occurred while fetching messages' })
      } finally {
        imap.end()
      }
    })

    imap.once('error', function (err) {
      console.error('IMAP Error:', err)
      res.status(500).json({ error: 'An error occurred while connecting to the mail server' })
    })

    imap.once('end', function () {
      console.log('Connection ended')
    })

    imap.connect()
  } catch (error) {
    console.error('Error:', error)
    res.status(500).json({ error: 'An unexpected error occurred' })
  }
}

async function fetchMessages(imap) {
  return new Promise((resolve, reject) => {
    imap.openBox('INBOX', true, (err, box) => {
      if (err) {
        reject(err)

        return
      }

      const messages = []

      const f = imap.seq.fetch('1:*', {
        bodies: '',
        struct: true
      })

      f.on('message', async function (msg, seqno) {
        const messageData = {}

        msg.on('body', async function (stream, info) {
          try {
            //store the body parsing promise in the array, ASAP
            messages.push(async () => {
              const buffer = await parseMessage(stream)

              return simpleParser(buffer)
            })
          } catch (error) {
            console.error('Error parsing message:', error)
          }
        })

        msg.on('attributes', function (attrs) {
          console.log('Attributes:', inspect(attrs, false, 8))
        })

        msg.on('end', function () {
          // console.log('Finished');
        })
      })

      f.on('error', function (err) {
        console.error('Fetch error:', err)
        reject(err)
      })

      f.on('end', async function () {
        console.log('Done fetching all messages!')

        // Wait for all body parsing promises to return.
        const parsedMessages = await Promise.all(messages)
        console.log('Done downloading all messages!')
        resolve(parsedMessages)
      })
    })
  })
}

function parseMessage(stream) {
  return new Promise((resolve, reject) => {
    let buffer = ''
    stream.on('data', function (chunk) {
      buffer += chunk.toString('utf8')
    })
    stream.on('end', function () {
      resolve(buffer)
    })
    stream.on('error', function (err) {
      reject(err)
    })
  })
}

Why are emails sometimes missing when making API requests for IMAP integration with Next.js? I attempted to use async/await methods, but they did not function effectively. This is my code where I'm attempting to retrieve all emails including headers and bodies. I'm missing more emails in production than localhost. The version of node-imap I'm using is "^0.9.6", and my Next.js version is "13.2.4"

Answer 1

import { simpleParser } from 'mailparser'

export default async function handler(req, res) {
try {
 const cred = req.body

 const client = new ImapFlow({
   host: cred.server,
   port: 993,
   secure: true,
   auth: {
     user: cred.email,
     pass: cred.password
   }
 })

 await client.connect()

 const mailbox = await client.getMailboxLock('INBOX')
 try {
   const messages = await fetchMessages(client)
   console.log('messages', messages)
   res.status(200).json(messages)
 } finally {
   mailbox.release()
 }

 await client.logout()
} catch (error) {
 console.error('Error:', error)
 res.status(500).json({ error: 'An unexpected error occurred' })
}
}

async function fetchMessages(client) {
const messages = []

for await (const message of client.fetch('1:*', { source: true })) {
 const parsedMessage = await simpleParser(message.source)
 messages.push(parsedMessage)
}

return messages
}

i have fixed that issue by replace the library node-imap == > imapflow imapflow

Answer 2

This happens because the fetch's end event is fired once it has sent you all the messages, but you put the messages in the list only once you have fully read their body, which does not have enough time.

async function fetchMessages(imap) {
  return new Promise((resolve, reject) => {
    imap.openBox('INBOX', true, (err, box) => {
      if (err) {
        reject(err)

        return
      }

      const messages = []

      const f = imap.seq.fetch('1:*', {
        bodies: '',
        struct: true
      })

      f.on('message', async function (msg, seqno) {
        const messageData = {}

        msg.on('body', async function (stream, info) {
          try {
            //store the body parsing promise in the array, ASAP
            messages.push(async ()=>{
                const buffer = await parseMessage(stream);
                returnt simpleParser(buffer);
            })
          } catch (error) {
            console.error('Error parsing message:', error)
          }
        })

        msg.on('attributes', function (attrs) {
          console.log('Attributes:', inspect(attrs, false, 8))
        })

        msg.on('end', function () {
          // console.log('Finished');
        })
      })

      f.on('error', function (err) {
        console.error('Fetch error:', err)
        reject(err)
      })

      f.on('end', function () {
        console.log('Done fetching all messages!');
        // Wait for all body parsing promises to return.
        const parsedMessages = await Promise.all(messages);
        console.log('Done downloading all messages!');
        resolve(parsedMessages)
      })
    })
  })
}

Here what we do is save the body promises in the array, that way we know what to wait for. We then wait for them before resolving the main promise.