[Python] Cannot communicate to SMTP server with socket and proxy due to timeout error

Here's my code for simple proxy validation:

import smtplib, socks

socks.set_default_proxy(socks.PROXY_TYPE_SOCKS5,
'*.*.*.*',
<PORT>,
username='<UNAME>',
password='<PWD>')

socks.wrapmodule(smtplib)
server = smtplib.SMTP('gmail-smtp-in.l.google.com', 25)
server.set_debuglevel(1) # SMTP dialogue log
server.ehlo()
server.quit()


Here's the output:

Traceback (most recent call last):
File "/Users/***/***/***/test.py", line 10, in <module>
server = smtplib.SMTP('gmail-smtp-in.l.google.com', 25)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/smtplib.py", line 255, in __init__
(code, msg) = self.connect(host, port)
^^^^^^^^^^^^^^^^^^^^^^^^
File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/smtplib.py", line 343, in connect
(code, msg) = self.getreply()
^^^^^^^^^^^^^^^
File "/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/smtplib.py", line 405, in getreply
raise SMTPServerDisconnected("Connection unexpectedly closed")
smtplib.SMTPServerDisconnected: Connection unexpectedly closed


I've pinged gmail-smtp-in.l.google.com – it's fine. I've also tried to check if we can establish connection with server through this proxy, and it seems like we can:

def test_proxy_connectivity(proxy, port):
ip, port_, user, pwd = proxy
try:
s = socks.socksocket()
s.set_proxy(socks.SOCKS5, ip, port_, username=user, password=pwd)
s.settimeout(5)
s.connect(('gmail-smtp-in.l.google.com', port))
s.close()
print(f'proxy availible {ip}:{port_}')
return True
except Exception as e:
print(f'proxy UNavailible: {ip}:{port_} - {e}')
return False

test_proxy_connectivity(PROXY.values(),25)


Output:

proxy availible <SAMEPROXYHERE>


So it kinda makes me believe that port 25 is open on this proxy. And if we add recv there:

def test_proxy_connectivity(proxy, port):
ip, port_, user, pwd = proxy
try:
s = socks.socksocket()
s.set_proxy(socks.SOCKS5, ip, port_, username=user, password=pwd)
s.settimeout(5)
s.connect(('gmail-smtp-in.l.google.com', port))
s.recv(1024).decode(errors='ignore')
s.close()
print(f'proxy availible {ip}:{port_}')
return True
except Exception as e:
print(f'proxy UNavailible: {ip}:{port_} - {e}')
return False

test_proxy_connectivity(PROXY.values(),25)


Output:

proxy UNavailible: <SAMEPROXYHERE> - timed out


The same problem I guess... And as far as I know this IP isn't in any blacklist like Spamhaus.

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