Question on windows server 2003

I?ve just installed windows server 2003 on the server in our company, as NAT server, mail server, web server, and FTP server. The old system on that server was windows server 2000, and all services had been working properly.
However after installing windows server 2003, I cannot access our server at home through broad band connection, either web site, mail server or FTP service. Is it because the security level of windows server 2003 is by default much higher than windows server 2000? While in the company, that is, within our LAN, NAT service has been working well. Is windows server 2003 by default refusing access from external area?