Really stuck with the Outlook?

Situation: NT SBS 4.5 server. 6 machines connected to it on a domain.
All suck internet through a LAN broadband router.

Server used to be configured on a modem dial-up and emails worked
fine. Now with this new ADSL setup (new provider) emails get stuck on
despatch. Finding the SMTP server configuration has been a task I
didn't manage. Can anyone help? I can only find the SMTP settings for
the administrator on the server but that is of no use? I found a
setting where all mail is forwarded to an internet based server but no
place for a password or login.

Then this outlook calendar? 4 PCs are configured to share the Calendar
and contacts function and 1 running outlook 2000 supposedly connects
to the exchange but will not share anything (no firewalls that block
it).

Finally the biggest insult? 1 PC is a laptop with VPN. It can connect
to the LAN (via Vigor 2600 broadband router) and will happily ping
internal PCs on their IPs but I cannot make it log onto the domain and
also the same problem with the outlook (but 2002 this time).

This is really driving me mad. If anyone can help I am prepared to pay
20 GBP for it via PayPal, NOCHEX, FastPay or directly into the bank.

Thanks