It's probably worth calling out that this is an experimental feature, and we are happy to get any and all feedback on things we can build out around them.

They are real numbers, not VOIP. That can matter depending on what they are used for and if the entity you are expecting a message from blocks sending to VOIP numbers.

The numbers don't rotate like our identifier rotation. They are yours. You can choose to delete a secondary number in the app, and if you have less than two, create a new one after 30 days.