What's the best way to handle staging and production environments?
We recommend to first connect your staging site to test the extension. Once testing is complete, connect your production site to the same MageMail account.
We generally haven't found a need to have ongoing separate accounts for staging and production. However, if you want to go that route, simply create a separate account (perhaps example_staging vs. example), and then connect example_staging to your staging site and vice versa.
Note that if you connect staging to your MageMail account, and then subsequently connect production, the previous connection from staging will be disconnected.