From 8e37f6068604dac2f25885db92143b6d0711b3a7 Mon Sep 17 00:00:00 2001
From: Hadley <hadley@foxular.net>
Date: Wed, 22 Feb 2017 19:22:54 -0800
Subject: [PATCH] Make generated message IDs for emails less likely to upset
 spam filters

---
 src/calibre/utils/smtp.py | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/calibre/utils/smtp.py b/src/calibre/utils/smtp.py
index e6ad2e9363..6c7da2f3b2 100644
--- a/src/calibre/utils/smtp.py
+++ b/src/calibre/utils/smtp.py
@@ -18,17 +18,24 @@ def create_mail(from_, to, subject, text=None, attachment_data=None,
     assert text or attachment_data
 
     from email.mime.multipart import MIMEMultipart
-    from email.utils import formatdate, make_msgid
+    from email.utils import formatdate
     from email import encoders
+    import uuid
 
     outer = MIMEMultipart()
     outer['Subject'] = subject
     outer['To'] = to
     outer['From'] = from_
     outer['Date'] = formatdate(localtime=True)
-    outer['Message-Id'] = make_msgid()
     outer.preamble = 'You will not see this in a MIME-aware mail reader.\n'
 
+    # generate a Message-Id for this email
+    msgid_domain = from_.partition("@")[2]
+    if not msgid_domain:
+        # from address didn't provide a domain, let's make a best guess
+        msgid_domain = safe_localhost()
+    outer['Message-Id'] = "<{0}@{1}>".format(uuid.uuid4(), msgid_domain)
+
     if text is not None:
         from email.mime.text import MIMEText
         if isbytestring(text):