See https://support.mozilla.org/en-US/questions/1463229

Thank you for the quick reply. That does not help my issue. My problem is not stopping sound notifications, it is that I get the initial notification for a new email as I should. But then I continue to get additional notifications for the same email about every 5 minutes or so after that. I just want to receive 1 notification when a new email arrives and that's all. Is there a way to stop the multiple sound notifications for the same email? Thank you again for your help.

Does this happen for every new message or only one? Does the same thing happen in safe/troubleshoot mode (hold Shift when launching TB)?

Sorry if I'm not giving enough detail. I have the settings to send a sound notification when a "new" email arrives. I then minimize TB so it just appears in the system tray as an icon. When I receive 1 new email, I get the sound notification and it shows on the icon there is 1 new email. Everything is fine to this point. I do not touch my computer at all. No new emails come in. The icon in the system tray still shows 1 new email. After about 4 or 5 minutes, I get another sound notification like I received another email. Nothing else changes. A few minutes later I get another sound notification. No new emails and the icon still shows 1 new mail. This continues until I open the app and actually click the email to show it read. Once I do that no more notifications, everything is fine. I kept thinking there might be a setting for play sound only once when emails arrive, but if there is, I can't find it. Hope this explains what's going on better. Thank you again for the help...