[stunnel-users] Connect using TLS with public Web Server

Hi All, I have older application and now I need connect with external server HTTPS using TLS . My application doesn't support with TLS and I think use Stunnel to connect with this Server HTTPS. Wich is the mode I should choose to configurate this connection ? Proxy mode? or like examples created over gmail in default configuration File?

The external server , is public server for all people ? should be necesary special certs ? or whit predeterminate certs inside windows (for use IE, chroome , firefox etc..etcc) is necesary ?

Many thanks

Regards