I have checked "Show an alert" and "Play a sound" under "When new messages arrive" in Thunderbird Preferences -> General. The "Play a sound" works, but "Show an alert" feature doesn't appeared. Based on these solutions https://support.mozilla.org/en-US/questions/997744 and https://support.mozilla.org/en-US/questions/991323, I have tried all combinations, but the results are all same "sound and no alert": mail.server.default.use_condstore;false & mail.imap.use_status_for_biff;false ==> sound and no alert mail.server.default.use_condstore;false & mail.imap.use_status_for_biff;true ==> sound and no alert mail.server.default.use_condstore;true & mail.imap.use_status_for_biff;false ==> sound and no alert mail.server.default.use_condstore;true & mail.imap.use_status_for_biff;true ==> sound and no alert Is there alternative solution for me?