The following is new behavior on Windows 10 -- I have been using thunderbird for a really long time: I cannot get thunderbird to stop making a sound on email arrival. This is annoying enough that I am now considering other email readers. I think that this started with the most recent update, but not exactly sure (at first, I thought something else was making these annoying sounds, so didn't really pay attention to email). I have tried turning off sounds *and* alerts in the general options (although I would prefer to keep the popup, removing sound is worth losing that feature). I have tried going into the system menu on Windows 10 to turn off "Desktop Mail Notification", "New Mail Notification", and (just for good measure), "New Fax Notification", and "New Test Message Notification". After all this mess, now I *sometimes* get the delivery sound. Like when I test by sending a message to myself. It doesn't always seem to make the noise, since some emails come in the background without making the sound. Of course, it no longer pops up the alert window (which I was somewhat fond of). I've tried killing and restarting Thunderbird. Any thoughts? The only thing I haven't tried is rebooting my machine after changing the system options, which I will when I can spare the time. Ack!