root email route unknown destination

Hi, I have a VPS hs01.domain.com and I've updated the contact manger email to support@domain.com and in preferences I've choose root to be the main destination for emails, but sometimes when I check in Email Delivary Reports I see root@hs01.domain.com as reciept but support@hs01.domain.com as the deliver where other field title "user" name support !! Where are these users come from? .. And is there a way to get access for email of the host ? I've check the contact manager and preferences many times but didn't find such that setting, what do suggest ? I have emails in Email Delivery Reports not exist in support@domain.com where root suppose to point to.