Explicit support for In-Reply-To / References in EmailMessage

[David Gilman]

If you want email clients to thread a response you need to set the In-Reply-To and References headers in the email with the Message-ID of the email you're responding to.

Right now, with the EmailMessage class, you can set both directly via the headers= kwarg. However, maybe it is worth an explicit kwarg, like it already has with cc, bcc and reply-to, to save the user the hassle of looking up the relevant RFCs and figuring out what needs to be done. It is a little bit of a weird case in that you have to set two different headers to what is usually the same value.

[Mariusz Felisiak]

Thanks for the ticket, however, headers is the right place to add in-reply-to, we don't want to add extra kwargs for all available headers. This API is generally frozen.