Are you using a static IP for your external NIC from Telkom? How have you setup your server to recieve email. Does it go and fetch it from your ISP or does your ISP spool your mail and push it out to your server? I have setup remote access quite successfully on our SBS 2003 R2 server in my office but we are using a static IP with IS. You dont need to create a VPN to fetch mail. If your users are using Outlook Exchange Client then setup their laptops to connect using RCP over HTTP. Otherwise you can always retrieve mail through Outlook Web Access.
Cheapest is to configure dynamic DNS (www.dyndns.org) for your SBS2003. Run the 'connect to the Internet' wizzard from the Server Management Console and allow Email and Remote Web Workspace on the firewall and configure your web server certificate for the dynamic DNS. Use the POP3 connector to deliver email to the user mailboxes. Setup your remote desktops to connect with HTTP over RPC or use the Outlook Web Access from the Remote Web Workspace (sbsdyndns.example/remote).