After starting the PC and launching Thunderbird, a connection to the server is established and the mails are also displayed in the inbox. With every further attempt, whether automatic or manual after starting Thunderbird, no mail is displayed in the taskbar at the bottom. I have switched off Norton 360 and also NordVPN but the problem persists. It also doesn't work when I close and reopen Thunderbird, I need to restart the PC and then it only works once again.