Yes, that sounds right. Anyone should be able to send mail to the server for any user on the server like you or your wife from anywhere on port 25. Only your local net should be able to send email to to the server for any destination. That is, mail relay is allowed but only from local net.

My mailserver only allows relay from localhost, so I have the stunnel connection from client to server so it thinks I am on the machine and can relay anywhere.

Web mail is also a good option in case your ever away needing to check or send mail. You can have a secure webserver on pot 443 running open webmail or something like it. Any computer that has a current browser can be used to connect to it and access email services and other file folders on the server.