outlook WAN question

[steve]

I have outlook 2000 users on a AD domain with Exchange
2000. They kept complaining about how slow it was to pull
down attachments over the WAN link. I did some packet
sniffing and found out that Exchange/Outlook was only
using about 70-80% of the bandwidth. To test to make sure
it wasnt the WAN link I did a file copy across the link
and it spiked all the way to 95-100%. Any reason why
Outlook/Exchange does not do this? Is there something
wrong?

Thanks!