1. Disable Extensions

Sometimes, browser extensions can interfere with website loading. Try disabling all extensions to see if that resolves the issue:

   Click on the menu button (three horizontal lines) in the upper right corner.
   Go to Add-ons and Themes.
   Disable all extensions by toggling them off.
   Restart Firefox and check if the webmail loads.

2. Check Firefox Settings

Make sure that certain settings in Firefox are not blocking the website:

   Disable Enhanced Tracking Protection:
       Click on the shield icon in the address bar when you are on the webmail page.
       Toggle off Enhanced Tracking Protection for that site.

   Check Content Blocking Settings:
       Go to Settings > Privacy & Security.
       Under Content Blocking, ensure that it is set to Standard or adjust the settings to allow the site.

3. Try Safe Mode

Running Firefox in Safe Mode can help determine if the issue is caused by settings or extensions:

   Click on the menu button, go to Help, and select Troubleshoot Mode.
   Click on Restart when prompted.
   In the Troubleshoot Mode, try accessing your webmail again.

4. Check Network Settings

Ensure that your network settings in Firefox are correct:

   Go to Settings > General.
   Scroll down to Network Settings and click on Settings.
   Make sure that No proxy or Use system proxy settings is selected.

5. Reset Firefox

If the issue persists, you can try refreshing Firefox, which restores it to its default state while saving your essential information:

   Click on the menu button, go to Help, and select More Troubleshooting Information.
   Click on the Refresh Firefox button.

6. Check for Malware

Sometimes, malware can interfere with browser functionality. Run a full system scan using your antivirus software to ensure your system is clean. 7. Create a New Profile

If none of the above solutions work, creating a new Firefox profile can help:

   Type about:profiles in the URL bar and press Enter.
   Click on Create a New Profile, follow the prompts, and then launch the new profile.

8. Reinstall Firefox

As a last resort, you can uninstall and then reinstall Firefox. Make sure to back up your bookmarks and any important data before doing so.

Before trying #1, I tried #3 (that worked). So, then I tried #2 and that did the trick.

I've never intentionally toggled the Enhanced Tracking Protection, so I don't know how that happened. But I'm so glad that it was something that simple instead of going through all my extensions.

Thank you so much for such a thorough list of things to try. This is definitely going into Evernote for future reference.