From eace9bd85257ebb0e9d2d9f61cff0cb25f1dae28 Mon Sep 17 00:00:00 2001
From: ale <ale@incal.net>
Date: Wed, 19 Mar 2025 11:10:54 +0000
Subject: [PATCH] Resolve the SMTP hostname on each connection
Combined with randomization of multiple results, this allows Mailman
to run simple round-robin balancing of the available SMTP servers.
---
Mailman/Handlers/SMTPDirect.py | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/Mailman/Handlers/SMTPDirect.py b/Mailman/Handlers/SMTPDirect.py
index 2e5963ca..7a9e8315 100644
--- a/Mailman/Handlers/SMTPDirect.py
+++ b/Mailman/Handlers/SMTPDirect.py
@@ -28,6 +28,7 @@ for a threaded implementation.
import copy
import time
+import random
import socket
import smtplib
from base64 import b64encode
@@ -55,13 +56,29 @@ except NameError:
+# Resolve host/port, randomizing multiple IPs.
+def _resolve(host, port):
+ results = [x[4] for x in socket.getaddrinfo(
+ host, port,
+ family=socket.AF_INET,
+ type=socket.SOCK_STREAM,
+ proto=socket.IPPROTO_TCP)]
+ return random.choice(results)
+
+# SMTP class that resolves the target randomly on each connection.
+class SMTPRR(smtplib.SMTP):
+
+ def _get_socket(self, host, port, timeout):
+ host, port = _resolve(host, port)
+ return socket.create_connection((host, port), timeout)
+
# Manage a connection to the SMTP server
class Connection:
def __init__(self):
self.__conn = None
def __connect(self):
- self.__conn = smtplib.SMTP(
+ self.__conn = SMTPRR(
local_hostname=mm_cfg.SMTP_HELO_HOST)
self.__conn.set_debuglevel(mm_cfg.SMTPLIB_DEBUG_LEVEL)
self.__conn.connect(mm_cfg.SMTPHOST, mm_cfg.SMTPPORT)
--
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