I’ve had a look and I don’t think this would be doable in the CRM, out of the box.
I’ve, so far, been unable to find a way to separate the Notification Emails from other System Emails, (as they all use Admin->Email Settings)
Unless anyone else can think of anything?
If it were to be customized, I imagine that this would require changes to the file at: modules/Activities/EmailReminder.php
I’m not entirely sure how to go about it, but as far as I can tell, the “sendReminders” function at line 131 is where the functionality resides, if you wish to take a look at it from a Code-change perspective?