I developed small Qt App for sending mails over smtp 465 port. It works on my developer linux mint 19.2 machine. When I deploy the app with all the libs to Mint 17.3 machine I get QAbstractSocketError::HostNotFoundError. I am using QSslSocket.
If I deploy my app and libs to another linux mint 19.2 machine it work without any problems. So the problem is the difference in mint 19.2 and 17.3. I exhausted all my possibilities/ideas.
p.s.
The OpenSsl is the same installed on both machines!