We provide cmail delivery for external clients from several different domains.
We rewrite the envelope sender (AKA: "SMTP
MAIL FROM","Return-Path" ) using a form of VERP. Thus we receive all the late bounces and have responsibility to forward them on to the original envelope sender.
These NDRs have no domain in the envelope sender so SPF does not apply, but it seems that these messages could fall foul of DMARC when we attempt to re-deliver them.
On these received NDRs should we be re-writing the
From: email header to
email@example.com or should we leave it as-is?