Error occurs while sending or receiving email on Outlook 2007.

I am experiencing this problem for the second day now. Whenever I try to send an email or somebody sends me an email on Outlook 2007, I can not send or receive it and an error occurs. At first I thought maybe the servers are down but it's the second day now and the same problem is happening. Is this an issue with my Outlook account? Can firewall be the reason for this? Will reinstalling Outlook fix the issue?
