[emersion]

> The ML server will verify the original authors SPF. The N recipients will verify the ML servers SPF - the chain (which matches the series of MTA's involved) is still verified end to end.

The recipients have no way to check that the mailing list server has checked SPF/DKIM/DMARC. Mailing lists very rarely drop messages because of a failing SPF/DKIM/DMARC check.

ARC tries to fix this, but requires recipients to trust the mailing list server. Just using plain DKIM is much better, recipients can just treat ML-forwarded emails just like direct emails.