Delegates function won't work in branch office

[Millie]

Hello,

Problem:

The home office users are set up as Delegates in the
branch office users' Outlooks with Editor permissions
(Tools... Options... Delegates), and the branch office
users are set up as Delegates in the home office users'
Outlooks.

The home office users can only access another home office
user's Inbox, but not a branch office user's Inbox.

The branch office users can only access another branch
office user's Inbox, but not a home office user's Inbox.

How can I fix this so that home office users can access
branch office users' Inbox and vice versa?

Network Information:

-Exchange 2000 Server running on a Windows 2000 Server in
the home office
-home office network on segment xxx.xxx.1.xxx
-branch office network on segment xxx.xxx.0.xxx
-branch office accesses Exchange 2000 Server via VPN
(dialup network connection on each computer)
-both offices have an ADSL connection with their local ISP
-branch office has a NetGear FVS318 Cable/DSL ProSafe
VPN/Firewall which also is the DHCP Server for the branch
office

Please let me know if you need more information.

Thanks for your help,
Millie