Outlook MAPI connectivity to Exchange

[MattFoster]

Hi,

I've been using VBox for a good while now, and am very happy with it.
However about 2 months ago I switched my host platform from Ubuntu to OS X.

Since then my Vista Enterprise 32bit client has been unable to talk to Exchange.
Doesn't matter if it is NAT or host networking, airport or wired, the connectivity is never established.

I'm at a bit of a loss as to what is going on here - does anyone have a working configuration with OS X host where Outlook 2K7 will talk MAPI to Exchange 2K3?
A casual wireshark analysis shows the client gets stuck trying to to DCERPC to the the Exchange server, and keeps on retransmitting them - packets which the host never sees.

If I hook to a public network, and fire up the VPN client in the Vista Guest, then the connectivity to Exchange is fine, but native connectivity seems to be a non starter.

Hints, tips & pointers would be appreciated.

Thx,

Matt