Were you aware that Thunderbird was running? That is you closed it earlier and there is still a process running without an open window. Perhaps hung there.

Or is this when you have Thunderbird open, but it is not responding for some reason?

Thunderbird was running, and typically is, when the computer is on. When clicking a Mailto link on any browser I get that error message and have to close TB before any emails can be sent. Then I have to restart TB to get to where I was.

Sorry, I just checked other browsers and the issue is only when clicking links within Firefox.

Sorry, I just checked other browsers and the issue is only when clicking links within Firefox.

Did you fix it in FF? I have the same issue.

I still have the issue and have not received any other replies.

I still have the issue and have not received any other replies.

I asked a question, you did not reply. I guess that is because you decided a conversation was not going to happen. Don't expect replies if you don't answer questions.

Matt, I sent a reply 5 minutes after you asked the question: Thunderbird was running, and typically is, when the computer is on. When clicking a Mailto link on any browser I get that error message and have to close TB before any emails can be sent. Then I have to restart TB to get to where I was. Then I corrected it with another reply: "Sorry, I just checked other browsers and the issue is only when clicking links within Firefox."