We have a network of about 25 Macs connected through a router to a large PC WAN. Several times a day, I find that all of our Macs seem to freeze for about 30 seconds. During this time the double-arrow icon appears steadily in the upper left, as if some network traffic is going on. The cursor does move, but all other actions are just queued up until the freeze goes away. P.S. We are also using MS Mail.