EmailMessage encode the subject in base64 when translated and contains non US-ASCII characters

[Yann]

The usual behavior of the EmailMessage class regarding its subject is to keep it as it is if i contains only US-ASCII characters and to encode it as quoted-printable if it contains non US-ASCII characters.

That works well and avoid our emails to be considered as pishing by antispam from email servers

But in the specific context of translations there is a bug -> if the subject of an email is translated into another language (through the built-in django translations tools) and contains non US-ASCII characters, by an mechanism I didn't catch, the subject is encoded as base64 and not quoted-printable.

This results in being considered as spam by the email servers (tested on Gandi and Gmail)...

[Mariusz Felisiak]

Thanks for the report. However I cannot reproduce this issue with the following test:

tests/mail/tests.py

@@ -28 +28 @@
 from django.core.mail.message import BadHeaderError, sanitize_address
 from django.test import SimpleTestCase, override_settings
 from django.test.utils import requires_tz_support
-from django.utils.translation import gettext_lazy
+from django.utils.translation import gettext_lazy, override
 from django.utils.version import PY311
 
 try:
@@ -1232 +1232 @@
             message.get_payload(decode=True).decode(), "Je t'aime très fort"
         )
 
+
+    def test_send_unicode_lazy(self):
+        email = EmailMessage(
+            gettext_lazy("Password reset"),
+            gettext_lazy("Password reset sent"),
+            "from@example.com",
+            ["to@example.com"],
+        )
+        with override("fr"):
+            num_sent = mail.get_connection().send_messages([email])
+            self.assertEqual(num_sent, 1)
+            message = self.get_the_message()
+            self.assertEqual(
+                message["subject"],
+                "=?utf-8?q?R=C3=A9initialisation_du_mot_de_passe?=",
+            )
+            self.assertEqual(
+                message.get_payload(decode=True).decode(),
+                "Message de réinitialisation du mot de passe envoyé",
+            )
+
     def test_send_long_lines(self):
         """
         Email line length is limited to 998 chars by the RFC:

Can you provide a sample project or a test case?