Avast Complains that Port 25 is blocked

I installed Avast and Avast complains that port 25 is blocked or already in use. This is not a problem on other PC I have installed AVAST on and I certainly don’t have port 25 intentionally blocked. OUtlook was successfully sending email prior to the installation of Avast!

I am running WinXP with Outlook (although I have seen this problem with Outlook Express as well).

I am on a small network with a NAT router.

What is happening and how do I eliminate the error message?

Use TCP View to found what application is blocking the port 25 (maybe a spam killer?) :wink:
Can you post the results?