Exchnage Server is unreachable

Hi,
I am running a Microsoft Server 2003 with exchange 2003 and currently not getting ANY SMTP inbound/outbound/internal. I went to check the server, and I noticed that the server is liseted as “unreachable”. could anyone suggest what might be the problem/ how to fix it? I’m really stumpted.

Thanks,
chuck.

To clarify:
Running Exchange 2003 Standard Edition on Wnidows SBS Server 2003
Exchange Information Store is not running and will not restart.
The following errors are appearing in the event log: MSExchnageSA 9098, MSExchangeFBPublish 8179, MSExchangeIS 9538, MSExcangeIS 5000.
IIS 6.0 is also installed and running.

Any suggestions/ ideas would be great.