To get approved to "read_page_mailboxes" permission please complete notes in Facebook developer console.
Details to be filled in textarea:
- Go to https://app.rubo.io
- Login with credentials, email: {your emails}, password: {your password}
- Click on one of the project.
- Click on “Reengagement”
- Click on “Campaigns”
- Click on “Add new campaign”
- Configure campaign.
After filling all details click Save button.