Currently, all email notifications come from a generic address like "Notifications@(sub-account URL)." The setting for the main account reply to address doesn't seem to roll down to the sub-accounts at all. Any replies to that email address don't go anywhere, either, so learners can send an email off to nobody.
It would be nice if at least the reply to address rolled down to the sub-account. Ideally, we could set the reply to address individually for each sub-account as well.