Hi Support, A customer uses Thunderbird as their main mail platform but suddenly cannot send or receive messages. error message as follows: Sending message failed. The message could not be sent because the connection to the SMTP server timed out. Try again. we get this message directly when we click send (1ms) Now we checked our Mail Server, connection is up also TLS to port 587 works fine but the client can not establish a connection... it worked a few days ago tho. We also tried to reinstall Thunderbird, new profiles and also tried debugging but we could not find the mistake. BR, Jakob Jauk