i've already configured my firewall (both the router and windows firewall) to work with SMTP at both port 25 and 2500, but my email still won't be sent - i tried it in outlook, and it goes fine, but nothing is sent; i tried it from a C# ASP.NET application, and i get this message in the inetpub/mailroot folder "failed to send the message to <email>" what else can i do?

Connect your PC directly to the Internet port and see if Outlook will work: If you get the same error message it's not your network. I kind of think it's not: You don't NEED port forwarding to send email. Firewalls filter INCOMING packets unless you have one that (manually) can be configured to deny outgoing traffic from unauthorized programs. Check with your ISP to make sure you have Outlook configured properly to work with their mail server. They usually have a tutorial.

this is my own mail server - the error message doesn't occur in outlook - it's a message in the inetpub/mailroot folder i'm still lost - iv'e got port 25 open on all firewalls - and also 2500 - but it won't go through - it "peacfuly" fails

Have you tried running the server directly off your gateway to see if it's really the firewall? Here's a really crazy idea: Contact your mail server's Customer Support and ask them what's going on.