Add forwarding headers to emails

[milescalabresi]

See "add forwarding headers" section of https://apps.google.com/supportwidget/articlehome?hl=en&article_url=https%3A%2F%2Fsupport.google.com%2Fa%2Fanswer%2F175365%3Fhl%3Den&assistant_id=generic-unu&product_context=175365&product_name=UnuFlow&trigger_context=a and add the appropriate headers to https://github.com/learning-unlimited/ESP-Website/blob/main/esp/mailgates/mailgate.py#L87.

[milescalabresi]

Added the headers suggested by Google but messages are still getting routed to spam in test. Could that be for some other reason, or is there more to do here?

[willgearty]

@milescalabresi was this ever resolved???