Can't set reply-to neither by header nor explicitly

[gomezjdaniel]

By running README example:

mail = EmailMultiAlternatives(
  subject="Your Subject",
  body="This is a simple text email body.",
  from_email="noreply@mydomain.com",
  to=["my@email.com"],
  headers={"Reply-To": "support@sendgrid.com"}
)
mail.send()

I get a 400 HTTP error

Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/usr/local/lib/python3.5/site-packages/django/core/mail/message.py", line 342, in send
    return self.get_connection(fail_silently).send_messages([self])
  File "/usr/local/lib/python3.5/site-packages/sgbackend/mail.py", line 68, in send_messages
    self.sg.client.mail.send.post(request_body=mail)
  File "/usr/local/lib/python3.5/site-packages/python_http_client/client.py", line 204, in http_request
    return Response(self._make_request(opener, request))
  File "/usr/local/lib/python3.5/site-packages/python_http_client/client.py", line 138, in _make_request
    return opener.open(request)
  File "/usr/local/lib/python3.5/urllib/request.py", line 472, in open
    response = meth(req, response)
  File "/usr/local/lib/python3.5/urllib/request.py", line 582, in http_response
    'http', request, response, code, msg, hdrs)
  File "/usr/local/lib/python3.5/urllib/request.py", line 510, in error
    return self._call_chain(*args)
  File "/usr/local/lib/python3.5/urllib/request.py", line 444, in _call_chain
    result = func(*args)
  File "/usr/local/lib/python3.5/urllib/request.py", line 590, in http_error_default
    raise HTTPError(req.full_url, code, msg, hdrs, fp)
urllib.error.HTTPError: HTTP Error 400: Bad Request

The thing is sendgrid-django has a set_reply_to method in the class Mail (https://github.com/sendgrid/sendgrid-python/blob/master/sendgrid/helpers/mail/mail.py#L154) while in sendgrid-django _build_sg_mail method (https://github.com/elbuo8/sendgrid-django/blob/master/sgbackend/mail.py#L69) reply_to is not added by the proper method, instead it expects to be added from setting a custom header like the example does:

for k, v in email.extra_headers.items():
    mail.add_header({k: v})

Next problem is django EmailMessage class only accepts reply_to param a list/tuple (https://github.com/django/django/blob/1c466994d9729a8902d34e277a3a685bef2a08e1/django/core/mail/message.py#L232) while sengrid-python expects only as I see one single email as reply-to (https://github.com/sendgrid/sendgrid-python/blob/master/sendgrid/helpers/mail/mail.py#L85 and https://github.com/sendgrid/sendgrid-python/blob/ca96c8dcd66224e13b38ab8fd2d2b429dd07dd02/examples/mail/mail.py#L132)

[kevin-brown]

This looks like it's probably the same bug as #34.

[gomezjdaniel]

It is. I already made a workaround fix -which miss the possibility that reply-to email includes a name- in a forked repository of this one that includes inside _build_sg_mail

        if email.reply_to:
            if isinstance(email.reply_to, str):
                mail.set_reply_to(Email(email.reply_to))
            else:
                mail.set_reply_to(Email(email.reply_to[0]))

Thing is Django asks as reply_to for a tuple/list while sendgrid only accepts one email as reply_to. Do you know if the email specification allows multiple emails in Reply-to header?

[abendig]

Our fix currently looks like this:

        for k, v in email.extra_headers.items():
            if k.lower() == "reply-to":
                mail.set_reply_to(Email(v))
            else:
                mail.add_header({k: v})
        if not mail.reply_to and hasattr(email, 'reply_to') and email.reply_to:
            mail.set_reply_to(Email(email.reply_to[0]))

Based on the discussion in #34 I can't tell how close an actual fix here is. Happy to help/contribute a PR for this though.