Thank you for your answer.
I have the server setup on one single IP. I'm using the IP to login to the web client.
Here is output:
Filesystem Size Used Avail Use% Mounted on
14G 3.5G 9.5G 27% /
/dev/hda1 99M 19M 75M 21% /boot
tmpfs 2.0G 0 2.0G 0% /dev/shm
But the strange thing is that when one of them are working the other is not. In each case I can't receive any emails in my account.