The "We Do Not Relay" error email - Sending an email and getting a returned message with that says it is undeliverable with "Non-local addressee. We do not relay!". Check here for possible solutions.
Microsoft Office Updates - If you use Microsoft Outlook (not express) as your email client, then you may want to make sure you have the most recent version with all the bug fixes and patches. To use Office Update, you may need to have your Office CD's available! After you click on the link, click on the button that says "check for updates".
Microsoft Outlook Express - This is the free email software that comes with most Windows computers (prior to windows Vista). To make sure you have the most recent version, you can run Windows Update or install the most recent version of Internet Explorer.