I would strongly consider setting up some kind of relaying via a VPN or SSH redirection so you don't need to relay from 0.0.0.0. That's opening a whole can of worms for the possibility of becoming a relay for others accidentally.
For example, if you're using a notebook computer, you could set up SSH to redirect local ports on the notebook to your SSH server on your home system, then you just run SSH first to create the redirects then configure your local mail client to connect to localhost for sending and getting mail. All traffic is encrypted between you and your server.
Or install and configure a VPN client on the server and notebook to connect to your home network.
There are bootable environments that you can take with you if you are looking at using computers from other locations that you don't own if you need to do some "custom" access from systems that aren't yours, depending on the situation, or you can set up a form of webmail to be served off your computer so you aren't exposing the mail server itself to remote relaying, you'd be doing it all from your webmail interface.