E-mail: "BadHeaderError: Header values can't contain newlines "

[LaurensBurger]

Product versie / Product version

2.3.0

Omschrijf het probleem / Describe the bug

Long subject lines (70+ chars) get \n added them and django-yubin will not allow the e-mail to be sent.
sentry: 336550
This results in a succesful submission: Registratieplugin "E-mail registratie" (email) meldt: Registratie geslaagd.

[sergei-maertens]

1. Report to upstream django-yubin
2. Contribute a patch - they are receptive

[SilviaAmAm]

What is happening:

• During queuing of message, django Yubin calls email_message.message() https://github.com/APSL/django-yubin/blob/master/django_yubin/__init__.py#L35 to get the message data as a string so that it can be saved to the database. When processing the headers, django core email module calls https://github.com/django/django/blob/main/django/core/mail/message.py#L74. This has the effect of adding \n characters to long subject lines.
• The resulting message is saved into the database (and it contains \n in the subject).
• When the queued task is picked up, the message is recreated from the string data before being sent https://github.com/APSL/django-yubin/blob/master/django_yubin/engine.py#L54, https://github.com/APSL/django-yubin/blob/master/django_yubin/models.py#L146. The checks for the new lines are done and they fail: https://github.com/django/django/blob/main/django/core/mail/message.py#L59

[SilviaAmAm]

Yubin PR: APSL/django-yubin#71