Closed Ports?
 

Hey Gang,
I came into work today only to discover that me and my coworkd can receive but not send email.
We use POP3/SMTP for our mail and the SMTP server is giving us problems while the POP3 or incoming mail works fine.

We've since called our ISP to try and resolve the problem however nothing has worked so far, the ISP can of course connect with the SMTP server but we can not.

I'm using SUSE 9.1 personal and my coworker WIN XP.
I was wondering if something happened that would have closed port 25, the port responsible for outbound email as far as I understand.
The weird thing is that both of us are seeing the same problem with our email client but we are using different operating systems.

What command would allow me to see which ports are open/closed etc?
Thanks

NMap is a port scanner that should allow you to do such.

The basic command would be nmap <ip or hostname>

It'll report either closed open or filtered. If it says that port 25 is filtered then it's most likely a firewall problem.