I want the Reply-to: header of all my outgoing email to have my pobox.com address, which forwards back to my icloud.com address where I collect my mail.
This discussion seems to raise the same question, and the answer is to use a terminal command, which is fine except it doesn't appear to have worked. New emails still come up with a blank Reply-to field. After I send it, and view all its headers in the Sent box, I don't see a pobox.com string anywhere; just a From: string with my usual icloud.com address.
(In case it matters: I want to be known by my pobox.com address since it's the one that's most likely to be permanent, and it's a pain having 5 or 6 abandoned email addresses for one person. So, this way I never need announce an email change, or have people wonder when I give them my pobox address but they received a reply from icloud.)