Pythoncom PumpMessages from different thread

I want to do something similar to what is asked here, but using threading like here. Using also the answer from here, I got my code working, only that an ItemAdd event is not recognised (actually, I think it is, but in the other thread, which is why there is no output).

"""Handler class that watches for incoming mails"""
import ctypes # for the WM_QUIT to stop PumpMessage()
import logging
import win32com.client
import sys
import threading
import time
import pythoncom

# outlook config
CENTRAL_MAILBOX = "My Mailbox"

# get the outlook instance and inbox folders
outlook = win32com.client.Dispatch("Outlook.Application")
marshalled_otlk = pythoncom.CoMarshalInterThreadInterfaceInStream(
    pythoncom.IID_IDispatch, outlook)


class HandlerClass(object):

    def OnItemAdd(self, item):
        logger.info("New item added in central mailbox")
        if item.Class == 43:
            logger.info("The item is an email!")


class OtlkThread(threading.Thread):

    def __init__(self, marshalled_otlk, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.marshalled_otlk = marshalled_otlk
        self.logger = logging.getLogger("OLThread")

    def run(self):
        self.logger.info("Starting up Outlook watcher\n"
                         "To terminate the program, press 'Ctrl + C'")
        pythoncom.CoInitialize()
        outlook = win32com.client.Dispatch(
            pythoncom.CoGetInterfaceAndReleaseStream(
                self.marshalled_otlk,
                pythoncom.IID_IDispatch
            )
        )
        user = outlook.Session.CreateRecipient(CENTRAL_MAILBOX)
        central_inbox = outlook.Session.GetSharedDefaultFolder(user, 6).Items
        self.logger.info(f"{central_inbox.Count} messages in central inbox")

        win32com.client.DispatchWithEvents(central_inbox, HandlerClass)
        pythoncom.PumpMessages()
        pythoncom.CoUninitialize()  # this is prbly unnecessary as it will never be reached


def main():
    # pythoncom.CoInitialize()
    OtlkThread(marshalled_otlk, daemon=True).start()


if __name__ == "__main__":
    status = main()
    while True:
        try:
            # pythoncom.PumpWaitingMessages()
            time.sleep(1)
        except KeyboardInterrupt:
            logger.info("Terminating program..")
            ctypes.windll.user32.PostQuitMessage(0)
            sys.exit(status)

I have tried various things, such as putting sys.coinit_flags=0 at the top, as suggested here), calling PumpWaitingMessages() in the main thread, and getting the Outlook application in the side thread itself, instead of passing the marshalled object. None of these have worked.

When I just put PumpMessages in the main thread (same HandlerClass but no separate thread) it works and emails are recognised upon arrival, but obviously the thread is blocked and not even the KeyboardInterrupt exception can be caught.

So, how do I get the outlook watcher running in the separate thread to send the messages to the main thread for output there?

from Pythoncom PumpMessages from different thread