From: de-mangling (DMARC) from local mails

[jluebbe]

Due to DMARC policies, some mailing lists and also the b4 http relay override the From: header. While in the b4 relay case, a From: is added in the body to keep git happy, this is not the case for many mailing lists. Google groups add an X-Original-From: header to preserve the original value. This is also done by the b4 relay.

Could b4 perhaps check if a X-Original-From: header exists and use that instead of the mangled From, to handle cases where the body doesn't contain an explicit From: and the mail is not fetched from public-inbox (--use-local-mbox)?