I wouldn't set it as my only outbox, I also use others. This is more of a l last ditch effort to make sure your notes can get out.
Outbox protocol works by clients knowing where your outbox is located, this information is part of your profile. They don't need to be configured, a client will connect automatically to the relay to retrieve your notes. This is all a work in progress as well, so ymmv
It also works for DM