You mentioned in your respons to Meinolf that you tried the SBS group? Which
group were you in? I was trying to find your post, but I did not have any
luck.
it is partially Windows specific because the inside NIC must have a static
IP. The reason is it is a server running numerous services that require a
static IP. That's the NIC with the Client for Microsoft Networks and other
components enabled.
Second, as Meinolf mentioned, since it is SBS, SBS does things differently
than regular Windows. The CEICW wizard is what sets it all up and if you
do not use the wizard, some things simply just do not work. But you
definitely need the internal NIC to have a static IP.
I am not sure what that DMZplus mode or even the name brand of the
router/firewall, but to have them tell you that for their firewall to work
that all machines must be set to DHCP is in my book, is unheard of. Active
Directory, the core component in SBS, cannot work that way.
I do not know what the firewall manufacturer had in mind with business
networks that use Active Directory and other services that rely on it to set
such a server to DHCP, unless they were thinking this feature is for a
workgroup, such as for non-Active Directory (AD) networks. Worse, my feeling
is the router's DHCP is providing the ISP's DNS addresses to the internal
machines, including the SNS server. SBS must be set to use itself for it is
DNS entry. Otherwise, this will cause numerous problems and is one major
cause of AD failure.
A quick AD rundown, AD relies on DNS. It stores all of AD's resource and
service location records (SRV records) in DNS. This is how SBS "finds" it is
own AD services and servers, as well as how clients "find" the domain when
they logon, authenticate to a printer, etc. If the ISP's DNS addresses are
used, no one can login, and AD cannot find itself becaues the ISP's DNS does
not have info about the internal AD domain.
Forgot to mention, Exchange uses and relies on AD. If AD fails, so will
Exchange, and a number of other services that rely on it.