Comment 8 for bug 1808301

AR header fields are generated on receipt, not transmission. All dkimpy does for this case is provide information to the calling application about if the signature verifies or not. It's not very complex to do. Look around line 320 in https://git.launchpad.net/dkimpy-milter/tree/dkimpy_milter/__init__.py for an example.

ARC though is looking for the previous recipient's AR fields, so you adding one isn't what it's looking for. As I said last time, I'd look at arcsign for a working example.