I seem to have some trouble understanding connection events

I connect to gmail and can open Inbox. It works to fetch emails. But the mail event gets only fired once at start, when i fetch mails, it does not get fired when i send a new mail.

imap.once('mail', function(numNewMsgs) {
	l('NEW MESSAGE', numNewMsgs);
});

also subscribing does not seem to have any effect. I have all connection events logging their args to console, but they never get fired. My understanding would have been, that not ending imap would keep the connection open and new mail to a subscribed box would trigger mail or update or any other event. But nothing happens. What am I getting wrong?

This is my whole testcode:

global.l = console.log;
import Imap from 'imap';
import { inspect } from 'util';

const imap = new Imap({
	user: '[e-mail]',
	password: 'xxx',
	host: 'imap.gmail.com',
	port: 993,
	tls: true,
	tlsOptions: { servername: 'imap.gmail.com' },
	debug: console.log
});

imap.once('ready', function() {
	imap.getBoxes(function(error, boxes) {
		if (error) throw error;
//l('BOXES', boxes);
		for (let box in boxes) {
			imap.subscribeBox(box);
			l('SUBSCRIBED TO', box);
		}
	});
	imap.openBox('INBOX', true, function(error, box) {
		if (error) throw error;

		var f = imap.seq.fetch('1:50', {
			bodies: 'HEADER.FIELDS (FROM TO SUBJECT DATE)',
			struct: true
		});
		f.on('message', function(msg, seqno) {
			console.log('Message #%d', seqno);
			var prefix = '(#' + seqno + ') ';
			msg.on('body', function(stream, info) {
				var buffer = '';
				stream.on('data', function(chunk) {
					buffer += chunk.toString('utf8');
				});
				stream.once('end', function() {
					console.log(prefix + 'Parsed header: %s', inspect(Imap.parseHeader(buffer)));
				});
			});
			msg.once('attributes', function(attrs) {
				console.log(prefix + 'Attributes: %s', inspect(attrs, false, 8));
			});
			msg.once('end', function() {
				console.log(prefix + 'Finished');
			});
		});
		f.once('error', function(err) {
			console.log('Fetch error: ' + err);
		});
		f.once('end', function() {
			//console.log('Done fetching all messages!');
			//imap.end();
		});

	});
});

imap.once('mail', function(numNewMsgs) {
	l('NEW MESSAGE', numNewMsgs);
});

imap.once('update', function(seqno, info) {
	l('UPDATE', seqno, info);
});

imap.once('expunge', function(seqno) {
	l('expunge', seqno);
});

imap.once('alert', function(message) {
	l('alert', message);
});

imap.once('error', function(err) {
  console.log(err);
});

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

imap.connect();

[mscdex]

Oh I see the issue now, you’re using imap.once() instead of imap.on(). Change that and you should see the new mail notifications.

[mscdex]

Actually subscribeBox() is a bit of a relic back when the creators of IMAP envisioned some sort of Usenet-like “mailbox” subscription experience.