Exchange OWA very slow on admin network
We have 2 separate networks - admin and curriculum, which are joined by a trust for access to sims on the curriculum.
Our exchange server has 2 network ports, with 1 each of the ports connected directly to each network. Email access via outlook web access on our admin network is very, very, very slow, whereas it's lightening fast (at least in comparison) on our curriculum network. However, accessing emails via the admin FR server, through OWA, is just as fast as it is on the curriculum; this, we imagine, would rule out config or bad cabling if it is fine on the admin network server (which connects to OWA the same way as the clients). We have tried moving admin workstations to our office (where the servers are kept) and the speed loading/accessing OWA is still the same - slow!
We are pulling our hair out over it, and our admin personnel aren't best pleased about it (understandably), especially when teaching staff have a perfectly fine email service. What could possibly be causing it, or where may be a good place to start looking?