diff --git a/libpius/mailer.py b/libpius/mailer.py
index 87ce05d..02aca7f 100644
--- a/libpius/mailer.py
+++ b/libpius/mailer.py
@@ -7,7 +7,7 @@
 import sys
 
 from email import message
-from email.utils import formatdate
+from email.utils import formatdate, make_msgid
 
 from email import mime
 from email.mime import multipart
@@ -385,6 +385,7 @@ def _send_mail(self, to, msg):
         else:
             msg["To"] = to
         msg["Date"] = formatdate(localtime=True)
+        msg["Message-ID"] = make_msgid()
 
         try:
             if self.ssl: