Thunderbird 68.1: Nothing happens when a link is clicked.
Tried Sandboxie 5.30 and 5.31.4
Older versions of Thunderbird work OK.
Of course Thunderbird 68.1 works fine without Sandboxie.
Using Windows 7 pro.
Fails the same on two different computers.
I have the same issue, no embedded link works anymore.
Sandboxie versions 5.30, 5.31.4 and 5.31.6 still all fail the same way.
Thunderbird is now up to 68.2.2 still fails linking to Firefox (70.0.1) and to Chrome (78.0.3904.97)
Links are dead. Do nothing. Links to open PDF's Docx etc all work OK.
System is Windows 7, but fails the same on my Windows 10 system.
Again, older versions of Thunderbird work OK with all versions of Sandboxie.
Sad that no one is looking into this.
Maybe, post your issue/s over on Wilders Security Forum to reach an audience of Sandboxie users.
Since 5.31.4 I had the same issue, so Sandboxie was my first suspect.
However, further testing showed that the problem persisted when Thunderbird was running outside the sandbox.
This seems to be an old issue with Thunderbird, as I found a working solution (from 2013) here: https://www.ghacks.net/2013/01/20/fix-for-thunderbird-not-opening-links/
A step-by-step description can be found on my own site: https://www.robvanderwoude.com/tweaks.php#ThunderbirdLinks
I hope this will work for you.
Your solution didn't work for me. Like others who have posted here, links don't work inside of Sandboxie, but work outside of Sandboxie. They also work inside Sandboxie if my default browser is Chrome. Oddly my config didn't have any network.protocolhandler.warn-external. booleans. I did create them and followed through with your instructions but it didn't help.
Something else must be going on. I posted earlier on this problem (https://community.sophos.com/products/sandboxie/f/forum/116410/firefox-won-t-open-links-from-thunderbird-email-program ) but didn't get any replies.
OS Windows 7 Pro 64-bit