This would be a configuration issue. My guess is your SMTP settings in your cart are not correct. Make sure you either remove the var/cache directory or rename it after you make settings changes. My guess is that given you have a dedicated server, you have permission issues which are preventing the cache from being cleared from the cs-cart application (I.e. using ?cc in the admin URL). Note in V2 you could clear the cache from customer or admin. In V4 it's only admin.