rpc over http-limits the number of users connected

[bz44]

When using Outlook 2007 to connect to sbs 08 w/ exchange 07 via "rpc over http" remotely I seem to have reached some limitation on the number of clients that can connect. I have one client that can not connect until another client disconnects from the server via the same type connection.
If this is performed locally inside the firewall, outlook uses a tcp/ip connection type and does it correctly. If you change the connection type to the "http" type when inside the firewall, you get the same results as remote users.
I can not find anything that details this type of limitation or how to increase the number of users connecting.
Any ideas?

[EINSTEIN_007]

RPC over HTTP works best in combination with Microsoft® Office Outlook® 2003 in cached mode. You should always use cached mode with RPC over HTTP to perform the following tasks:

• Reduce the number of connections that Outlook has to make to the Exchange server.
• Insulate the client from Internet latency.

More information here.

[bz44]

I have a very low number of users but I can't seem to find any reason why I can not get another to connect remotely using rpc over http in Outlook 07.
Does anyone know where I might find a limitation on connections for this?