You need to check which Smtp Server your provider uses.
You could find this out if you have an OutLook client configured.
Go to Accounts> Servers and check the entry under Outgoing mail. If you are using web-based email like Hotmail, etc then it's not as easy since they uses the HttpMail protocol.
Once you have the ip address then the rest is the same i.e
get a session, create your mail, get a transport object and

transport.sendMessage(msg,msg.getAllReceipients())