SBS 2008 (SBS2008) requires the following ports for complete functionality including Remote Web Workplace. Forward the following ports at your router or firewall:

• SMTP 25 - Simple Mail Transfer Protocol
  HTTP 80 - Home Page Web
  SSL 443 - Home Page Web Secured HTTPS (RWW, OWA, remote desktop or Terminal Server sessions)
  HTTP2 987 - Second SSL Secured on alternate port for SharePoint (optional)
  PPTP 1723 - VPN Connections

Port 4125 was required on SBS 2003 but this is no longer required as it is replaced by the Terminal Services Gateway which uses port 443 over HTTPS.  This is better as HTTPS is allowed nearly everywhere.