I am not an expert in how the email services works, so forgive me if it's obvious...
When/if I need to move the website to a different server I like to test if it works correctly before putting it online. So usually I upload files, install everything etc. and by editing my host file I can bypass current real DNS settings and access new server to test everything before switching DNS for the rest of the world. It's quick and easy - simple short entry in the host file.
Now I would like to do the same for email server. I would like to test if it will accept and forward in the way I want the incomming emails sent to addresses @ mydomain, but without changing the MX records, yet. I would prefer to find most easy and quick method for just 2-3 tests (from my local machine or from any other existing server) without need to spent too much time on installing too much software just for these 2-3 tests - if so I'll pass and take a risk that emails won't be delivered for a day.
Thanks.