Anca, my comment no longer stands because Sidali explained to me that we need a single email address to be used (for "spam" reason) and he's right. So the user should not be able to specify the email address to use for sure.

And if the admin email is not defined, it's not that important what email address is used too provided it's always the same one. So I now agree that what Sidali has code could work fine. I still have this little nag at the back of my head saying that it would still possibly be better that this features is active only if the admin has defined an email address but let's forget it for now...