Customarily, in the US, it is three days. Postal Police Officers (PPOs) are a crucial part of the Inspection Service team.Stationed in postal facilities across the nation, they stand on the frontlines. Application Process. 1. Pre-Screening. 2. Pre-Employment. 3. The application process takes approximately 90 to 180 days to complete and consists of six phases. This PPP covers violations of laws, rules, and regulations implementing merit system principles. Take your police exam with confidence.