To ensure that clicking on an email address opens Thunderbird instead of Outlook in Windows 10, follow these steps: Set Thunderbird as Your Default Email Client: Open the Settings app (press Windows + I). Navigate to Apps > Default Apps. Scroll down to the Email section. Click on the current default app (likely Outlook) and select Thunderbird from the list. Configure Protocol Associations (Optional): In the same Default Apps window, scroll down and click on Choose default apps by protocol. Look for the protocols MAILTO and EML. Set both to Thunderbird. Verify in Thunderbird: Open Thunderbird. Go to Tools > Options (or Menu > Preferences depending on your version). Under the General tab, ensure that Thunderbird is set as the default email client. If not, click Set as Default. Test on QRZ or Other Pages: Visit the page with an email link, click it, and it should now open in Thunderbird. If you continue experiencing issues, please provide more details, and we'll be happy to assist further! Best regards,