All smtp  servers should be set up to disable relaying outside of their
own network, making it impossible for you to relay through someone
else's mail server  without being on their network. Servers that are not
set up this way become spam gateways very quickly.

If you are trying to set up your own smtp client  then you should set up
your own server for testing purposes. There are plenty of free SMTP
servers for both windows and unix OSes.