SBS 2003 Exchange setup - ISP blocks SMTP port 25

[GHTTECH]

SBS 2003 (domain_name.local) installed and configured with Exchange. I can
send and receive messages to internal users on the Lan. I cannot
send/receive external messages to any users. My ISP blocks port 25 (AT&T).
I have a static IP address with AT&T. I have registered a domain name
(domain_name.com) with a hosting company other than AT&T. I've tried
diffferent suggestions found on the Net but have been unable to get it to
work. Any and all help would be greatly appreciated. Thanks

[Comprev]

Download and install a program called STunnel. It will run as a Service. Set
it to listen on an unused port. Set it to transmit on the necessary port and
address for your ISP using your user name and password.

Next, in the SMTP server settings, set the outgoing server to localhost
(it's been a while since I've set this up, but it works. I can't remember is
localhost is acceptable here, if not, enter your SBS Server's internal IP
address or FQDN, such as mycompany.local instead) and set the port to the
port that you set STunnel to listen on. No authentication should be needed.
As I said, it has been a while since I've done this and I'm not at the site
that I have this set up. I don't remember for sure if I set the user
name/password in STunnel's setup or if I simply told STunnel to make the
secured conenction and use the SMTP server's authentication to set the user
name/password and STunnel simply passed it through.

While I don't remember all the exact details, this problem does allow you to
make the connection and send email.