1. Verify that the Internet connection is active and working correctly. Check one of your favorite websites with your web browser to see if you are still connected. See if your browser says that it's working offline. Contact your Internet service provider to fix the connection problem if you are working offline.
2. Contact your ISP and request the correct settings for your email server. Verify the POP3 or IMAP settings in Eudora. Click on 'Tools,' select 'Options.' Check your settings for login name, mail server (incoming) and for the SMTP (outgoing) server. These must be correct. Even a simple typo will cause the error.

3. Use built-in operating system networking tools. There is a valuable network tool called 'ping.' This software tool sends a small message to another computer and sees if a response is sent back. Click 'Start,' select 'Run,' type 'cmd' and click 'OK.' Ping the IMAP server or POP3 server provided by your ISP to verify that your mail server is available. For example, you would type at the command prompt 'ping pop.yourmailserver.com.'
4. Disable your anti-virus software and test your email send/receive option. If you are able to receive messages, contact the virus scanner manufacturer and get instructions to add an exception for Eudora.
5. Check your firewall. Verify that your firewall is not blocking the 'ports' used by Eudora. Windows Firewall is often configured to block commonly used email ports to prevent malware from infecting your computer. Microsoft provides a guide for determining if your firewall is blocking the ports your Internet applications like Eudora need to operate.