Invalid security certificate to access SMPT of other server

Invalid security certificate to access SMPT of other server

Dear Team,
Getting invalid security certificate error to access smtp of other server. The other server smtp is fully accessible with gmail and others. A screenshot is attached. Please help


I'm fully aware that the port connection type is TLS and port is 25, as i was informed from my institute and is working with gmail. I's getting accepted with "Never" type but "relay error" is occurring when trying to send.
 
With Regards

Abhik