@hramezani Thanks for checking 👍

@felixxm can you cherry-pick this commit for django4.2 ? since this issue is appearing on python3.11.9 also.

@awais786 no, it doesn't qualify per our backporting policy

Scratch that, it was indeed backported 0d3ddca and should be part of the next 4.2.x release.

@awais786 no, it doesn't qualify per our backporting policy

Scratch that, it was indeed backported 0d3ddca and should be part of the next 4.2.x release.

Yes, we made an exception since this is a compatibility issue with supported versions of Python.

Hi all 😄 Does anyone know if there's a workaround until 5.0.5 gets released ?

Hi all 😄 Does anyone know if there's a workaround until 5.0.5 gets released ?

The next release for both 4.2.12 and 5.0.5 is planned for May, 6th. If you need a workaround sooner than that, you can apply the diff from 2e6ae1e in your Django installation.

Thanks @nessita !

For anyone else needing a workaround:

• Probably best option is to stick to a Python version which doesn't have the issue - I can confirm the issue isn't present in 3.11.8 (but appears in 3.11.9)
• Second best option is to patch Django installation as suggested by @nessita

Neither of these were simple for us due to the way our containers are build. Less ideal, but much simpler to implement, was to monkeypatch Django. Given that there is a known fix released in two weeks, we assessed it was ok to do so.

We monkeypatched from the ready signal of the relevant app's AppConfig:

from django.apps import AppConfig


class TheRelevantApp(AppConfig):
    default_auto_field = "django.db.models.BigAutoField"
    name = "therelevantapp"

    def ready(self):
        # This is a patch to fix this issue: https://github.com/django/django/pull/17979
        # The fix will come out with Django 5.0.5 on May 6th, so we should remove the patch
        # when we upgrade 
        import django
        from email import charset as Charset
        from email.mime.text import MIMEText

        utf8_charset_qp = Charset.Charset("utf-8")
        utf8_charset = Charset.Charset("utf-8")
        RFC5322_EMAIL_LINE_LENGTH_LIMIT = 998

        class SafeMIMEText(django.core.mail.message.SafeMIMEText):
            def set_payload(self, payload, charset=None):
                if charset == "utf-8" and not isinstance(charset, Charset.Charset):
                    has_long_lines = any(
                        len(line.encode(errors="surrogateescape")) > RFC5322_EMAIL_LINE_LENGTH_LIMIT
                        for line in payload.splitlines()
                    )
                    # Quoted-Printable encoding has the side effect of shortening long
                    # lines, if any (#22561).
                    charset = utf8_charset_qp if has_long_lines else utf8_charset
                MIMEText.set_payload(self, payload, charset=charset)

        django.core.mail.message.SafeMIMEText = SafeMIMEText

PS: this will fail if you use mypy and django-stubs, as the django-stubs plugin actually executes this code, but in that context django.core.mail doesn't exist ! You can fix that by only executing this code if hasattr(django.core, "mail")