Fine with me, but now it is required: Who is responsible for setting
that address in the owner-email? The implementation? The user? Is it
related to ":from"?
Since the point is to identify the sender, I suppose the implementation
is responsible for the values of owner or token
The point is not to identify the "sender"; it's to identify the owner of the
sieve script, and that's all made clear in section 2.7.1. Only the
implementation knows how to do that. I don't think there's more that needs to be
said there.
Barry