Using Mail Node / Disconnect before TLS was established

Hello together

I've got an question to the "mail" node...
It's working with gmail.
But I want to send with my local Mailserver and Port 25... Mailserver is an "OpenRelay"... No authentification and no encryption needed.

When I send a msg.payload to the mail node, I get "Error: Client network socket disconnected before secure TLS connection was established" from mail node.
"Use secure connection" and "Use TLS?" is both deactivated...

Any Ideas what I'm doing wrong?

Mailserver is Exchange 2007.
Thanks and Greetings