const Imap = require('imap');
let imap = new Imap({
  user: 'user@mail.ru',
  password: 'pass',
  host: 'imap.mail.ru',
  port: 993,
  tls: true
});

function imapConnect(imap) {

    return new Promise((resolve, reject) => {
        console.log('Connecting');
        imap.connect();
        imap.once('ready', resolve);
    });

}

function openInbox(name) {

    return new Promise((resolve, reject) => {
        console.log('Open inbox');
        imap.openBox(name, true, resolve);
    });
}

function getMessage(msgEE) {

    return new Promise((resolve, reject) => {

        let msgObj = {};
        msgEE.on('body', async (stream, info) => {
          msgObj[info.which] = {
            info,
            "data": await getStreamData(stream)
          };
        });
        msgEE.once('end', () => resolve(msgObj));
    });

}

function getStreamData(stream) {

  return new Promise((resolve, reject) => {
      let buffer = '', count = 0;
      stream.on('data', function(chunk) {
          count += chunk.length;
          buffer += decode(chunk);
      });
      stream.once('end', () => resolve(buffer));
  });

}

async function run() {

    await imapConnect(imap);
    await openInbox('INBOX/заявки');

    var f = imap.seq.fetch('1:10', {
      bodies: ['HEADER.FIELDS (FROM)','TEXT'],
      struct: false
    });

    f.on('message', async (msgEE, seqno) => {

        let msg = await getMessage(msgEE);
        console.log(msg);

    });

}

run();