Sent E-mail by C# code application getting error

Hello everyone.
Given that I am not an expert in Networking, I have imported my web domain in Cloudflare.
After Cloudflare had imported all DNS information from my domain provider, my application stopped to send e-mails and started to get this error:

  • A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond
    “at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress) at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Exception& exception)”

I don’t know how to set up the DNS in cloudflare or which SMTP client configuration I need to set up.
In my Aruba email pannel (it is my domain provider), I am not getting errors.

I hope to have described clearly the problem.

Just be clear, I am trying also to send email from my dev pc. It is not related to the Cloudflare.