Problem

Is it possible or not to change the default domain .

Resolution

It is possible following these steps in PassPort UI:

1. Go to Administration -> Products and select the product you want
2. Choose the 'default' instance
3. Go to Domains and select the domain you want to have as default
4. Press the 'Make Default' button and save

Optional if you want to eliminate the other domains you can click on them and press 'Delete'. If at any point you want them back on the list you can add them by clicking 'Add domain' and selecting them from the list.