Entourage, SBS2008 Exchange 2007

Hi, i have some users that have mac with entourage 2008, connecting to the exchange server (SBS2008 with Exchange 2007). When seting up the domain administrator on entourage everything work, but when using a normal user then i has to use remote.domain.no/exchange/user@domain as the exchange server BUT the problem is that its disconnecting every 3-5 min and thats stupid, but on the adminstrator account i can use remote.domain.no on the exchange server and its working perfect. What could i do to have the normal users use remote.domain.no thats working okey?