To make Firefox or Internet Explorer trust ECE root certificate:

1. Click Root Certificate for some ECE research groups
2. When a window is popped up, enable the first two options or enable all options , and click OK.
(I f  you use both Microsoft Internet Explorer and Firefox as your web browser, you may have to run the two step in both browser)

To make thunderbird trust ECE root certiifcate:

1. Right Click the link above,  Choose "Save link as ..." , and save the file to your desktop
2. Open your Thunderbird browser
3. Right click your account name in the left panel, and choose "properties"
4. Select "Security" under your account in the left panel of the new window
5. Select "View Certificates" button in the bottom of the right panel
6. Select "Authorities" in the top menu in the new window
7. Click "Import" button, and select the file you have saved in step 1.