Subscribe By Email, Sender?

I've invited several blog admins to try out the Subscribe by Email plugin. What I've noticed, that I didn't see on testing myself, is that the sender of the emails is from my primary site domain. A subscriber of blog with a mapped domain is not likely to recognize this sender and may spam the subscription.

Is there a way to modify the sender to be the blog admin (or domain) so the emails have a chance to be recognized by the subscriber to a mapped domain?