Peter, This is a known weakness in Groups.io - it accepts forged header From addresses. There were discussions about this years ago in beta associated with DMARC as a topic, and no Groups.io does not

Barry, Bruce said: That's a concern with the primary group, but I don't think it is with subgroups. I believe the owners of the primary group always have ownership privileges in all subgroups, even if

Brooke, I use a horizontal rule at the top and bottom of the custom portion, and a font different from the boilerplate, to help visually set it apart from the clutter. See Message 27136 Way back when

Christos, There's an exclusion from masking addresses in the groups.io domain. Because those are (were) never user addresses. This predates the munging of addresses for DMARC. So it appears that's a l