The mailing list for listmasters using Sympa

["John Levine" <address@concealed>]

It appears that Ralph Ballier <address@concealed> said:
>How can I restore the sender's address in the header so that the 
>recipient can reply directly to them?

You can't.  DMARC is unfortunately broken by design.  The best you can do is
copy the original address into Reply-To: but that screws up replies to the 
list.

I have a kludge implemented as a shim between sympa and the mail server that
rewrites addresses like this, e.g.

From: Marissa <address@concealed>

to this

From: Marissa <address@concealed>

I did some hackery in my msil server so that's a real address that forwards
back to the the original address for a few days, but that needs considerably
more control over your mail server's configuration than most list operators 
have.

R's,
John