Hello Carsten, i tested now with the "original" Thunderbird and there is no sound notification also. So this should be a general problem or a sound misconfiguration. I attached a screenshot for the sound configuration of the Thunderbird.
But how can i find the problem? All other sound is working! The file is playing perfect with any other soundplayer including "aplay siehabenpost.wav". Best regards Karsten
<<attachment: thunderbird.png>>
