Spoof a local mail server to bypass Outlook for Mac's mandatory sign‑in

Classic Outlook for Windows can be started without an email account via Outlook.exe /PIM <new-profile-name>.

Outlook for Mac does not offer an equivalent option, but this can be worked around by pointing Outlook at a local dummy mail server so it accepts account setup without real credentials.

1. Run a local dummy mail server

Save and run the following script:

import socket
import threading

RESPONSES = {
    'POP3': {
        'greeting': b"+OK POP3 server ready\r\n",
        'bye': b"+OK Bye\r\n",
        'default': b"+OK\r\n",
        'commands': {
            'CAPA': b"+OK Capability list follows\r\nUSER\r\nUIDL\r\n.\r\n",
            'AUTH': b"-ERR Authentication failed, try USER/PASS\r\n",
            'STLS': b"-ERR TLS not available\r\n",
            'STAT': b"+OK 0 0\r\n",
            'UIDL': b"+OK\r\n.\r\n",
            'LIST': b"+OK 0 messages\r\n.\r\n",
        }
    },
    'SMTP': {
        'greeting': b"220 localhost ESMTP\r\n",
        'bye': b"221 Bye\r\n",
        'default': b"250 OK\r\n",
        'commands': {
            'EHLO': b"250-localhost\r\n250-SIZE 1000000\r\n250 8BITMIME\r\n",
            'HELO': b"250-localhost\r\n250-SIZE 1000000\r\n250 8BITMIME\r\n",
            'DATA': b"354 Go ahead\r\n",
            'AUTH': b"235 2.7.0 Authentication successful\r\n",
        }
    }
}

def handle_connection(conn, protocol):
    cfg = RESPONSES[protocol]
    conn.send(cfg['greeting'])

    with conn:
        while True:
            try:
                data = conn.recv(1024)
                if not data:
                    break

                command = data.decode('utf-8', errors='ignore').strip().upper()
                print(f"[{protocol}] Received: {command}")

                if command.startswith("QUIT"):
                    conn.send(cfg['bye'])
                    break

                # Find matching command
                response = cfg['default']
                for cmd, resp in cfg['commands'].items():
                    if command.startswith(cmd):
                        response = resp
                        break

                conn.send(response)
            except (ConnectionResetError, BrokenPipeError):
                break

def start_server(port, protocol):
    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
        s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        try:
            s.bind(('127.0.0.1', port))
            s.listen(5)
            print(f"Listening on port {port} for {protocol}...")
            while True:
                conn, addr = s.accept()
                print(f"Connection from {addr} on {protocol}")
                threading.Thread(target=handle_connection, args=(conn, protocol), daemon=True).start()
        except OSError as e:
            print(f"FAIL: Could not bind port {port}. Error: {e}")

if __name__ == "__main__":
    servers = [
        threading.Thread(target=start_server, args=(1100, 'POP3'), daemon=True),
        threading.Thread(target=start_server, args=(2525, 'SMTP'), daemon=True),
    ]

    for t in servers:
        t.start()

    try:
        for t in servers:
            t.join()
    except KeyboardInterrupt:
        print("\nShutting down...")

2. Configure Outlook for Mac

In Outlook for Mac, create a new account with these settings:

Dummy email address and password
Incoming server: 127.0.0.1
Incoming port: 1100
Outgoing server: 127.0.0.1
Outgoing port: 2525
SSL: disabled for both incoming and outgoing

Notes

Legacy Outlook (equivalent of classic Outlook on Windows) and Work Offline options are located under the Outlook menu in the macOS menu bar.
Use Outlook Profile Manager, located at /Applications/Microsoft Outlook.app/Contents/SharedSupport/Outlook Profile Manager.app, to create or delete Outlook profiles and set the default profile.

❧ 2025-12-07