I configured mailto links to go to Thunderbird Portable. This works fine if Thunderbird is closed. However if Thunderbird is already open, then I get an error message when clicking on an email link: Thunderbird is already running, but is not responding. To open a new window, you must first close the existing Thunderbird process, or restart your system.
My registry settings for the mailto command --
Key: HKEY_CLASSES_ROOT\mailto\shell\open\command to:
Value: "r:\ThunderbirdPortable\ThunderbirdPortable.exe" "%1"
According to mozillazine you should only get this error if you are opening a second instance of Thunderbird displaying the main window. The second instance should open fine if it is launching a Compose window or the Address book.
Is this a limitation of Thunderbird Portable? Are there workarounds? I spent quite a bit of time researching this and didn't find any solutions.