Add support for html email messages through django.core.mail.send_mail()

[Justin Michalicek]

I have run into several instances where it makes sense to be able to send html email messages through django.core.mail.send_mail(). Allowing this would also be consistent with the mail_admins() and mail_managers() functions.

When adding this I did see that the comments for send_mail() say that the api is frozen. I had previously asked about this feature on the django-developers google group in this thread ​https://groups.google.com/forum/#!topic/django-developers/_mXKP9JZzK0 so I hope this is not a problem.

I have forked the repo and created a feature branch at ​https://github.com/jmichalicek/django/tree/add_send_mail_html_message which has the feature, updated documentation, and test cases.

[Tim Graham]

Given that Russ seemed to accept the ticket in the mailing list and was the one who committed the original change which included the comment about the API being frozen, I assume this is fine.

I left minor doc comments on the ​PR.

[Justin Michalicek]

Thanks, I've updated the docs as noted in the comments.

[Tim Graham <timograham@…>]

In ac0955876089002f0f60857d09fe1c94d67eca4f:

Fixed #20817 -- Added html_message parameter to django.core.mail.send_mail()

[Russell Keith-Magee]

For the sake of completeness -- yes, I've got the git blame attribution for the "frozen" comments, but I wasn't the original author. The original author of those comments was Malcolm d5d2072bbfc38015a93d6e13136c3f1dbf125d87. He made that change because the intention was to discourage people from using send_mail, and encourage the use of EmailMessage instead. The intention was that Django should only have the bare minimum tools for sending mail; if you wanted more, you should be using Python native features. We had a lot of feature requests on django-users/django-dev to add extra arguments to send_mail; the comment in the code was an attempt to stop those requests.

However, since that time, the world has changed a bit. We've introduced mail backends, which massively increased the scope of the mail APIs in Django. We fixed #10863, which added HTML mail functionality to some (but not all) of the internal mail sending tools. More generally, HTML mails have become a lot more common/acceptable.

[Tim Graham <timograham@…>]

In d4dd55e78ccc8d38de750313f75d6921137e71ab:

Doc tweaks for html_message parameter to send_mail(); refs #20817