Hi,
Only the main vendor could send a notification.
Regarding the current view, the limitation is not set
if(isset($this->edit) && $this->edit === true && hikamarket::acl('order_edit_notify')) {
Should be
if(isset($this->edit) && $this->edit === true && $this->vendor->vendor_id == 0 && hikamarket::acl('order_edit_notify')) {
A vendor could just update a partial order (a sub order) and, because it is not completely defined, I preferred to forbidden the mail notification for the vendors.
That's why you would find in the order class
if($vendor_id == 0 && !empty($data['notify']) && hikamarket::acl('order_edit_notify')) {
I guess that we can put an option but I can't yet guarantee that the result would be directly the right one.
Regards,