Quoting Nico Erfurth:
> "${if def:received_for{X-Envelope-To: <${received_for}>\n}}");
>
> If I'm not wrong, received_for can't be set while the mime/content ACLs
> are running, but I wasn't sure.
I don't know that, but according to the spec, it is only set if there is
exactly one recipient, which is bad. I sent a small patch to this list a
while ago, replacing it with $recipients. Nobody seemed to care about
it, though.