I can receive mail just fine, but any attempts to send mail through Thunderbird fail with this message. The only way that works for now is to save the draft and send it via Google/Microsoft web interface. As far as I know, my SMTP settings are correct, but posting them here just in case. Thunderbird version: 102.8.0 (64-bit) Linux: Ubuntu 22.04.2 LTS ISP: Lanet Antivirus/Firewall: none that I know of. I tried to use K9 to send the one of my drafts (using the wifi, i.e. the same internet connection) and got "Unable to open connection to SMTP server". Does that suggest that the problem is with routing and/or ISP? Help is appreciated.