Patch to add support for setting email return-path

[wreese@…]

Our Django application needs to send customized mail messages using
Variable Envelope Return Paths (VERPs - ​http://en.wikipedia.org/wiki/VERP ).
This simply means setting the return path of each outbound
email message to something unique, so that bounced messages can be
accurately tracked and handled.

In order to do this, developers need to be able to set the
"from_addr" parameter that is passed through to the sendmail() method
of the smtplib.SMTP class. Currently, Django automatically sets this
parameter based on the "From" header that is set on the EmailMessage
object.

The attached patch simply modifies the EmailMessage and
SMTPConnection classes to allow developers to manually set the return
path attribute, while safely defaulting to the "From" header (the
current default) if it is not supplied. The changes are minimal,
and tests and documentation have been written and supplied with the patch.

[wreese@…]

Patch to add support for setting email return-path

[Malcolm Tredinnick]

At the moment, I'm -1 on this. We made EmailMessage and SMTPConnection subclassable for exactly this reason: so that people with specialised requirements can make their own modifications without needing us to change the core.

Leaving open for a bit to think about it.

[Jacob]

I agree with Malcolm, so I'm marking this wontfox.

[Thomas Güttler]

related #9214