From Publication 166, U.S. Postal Inspection Service:
YOUR RISK LEVEL 3a
PHYSICAL SECURITY OF YOUR WORKPLACE
YOUR MAIL CENTER 8
EMPLOYEE ROLES AND RESPONSIBILITIES
MAIL THEFT 11
SECURING YOUR MAIL CENTER FROM THEFT
LETTER OR PACKAGE BOMBS AND BOMB THREATS 13
ESTABLISH A SECURITY AND BOMB-SCREENING PLAN
CHEMICAL, BIOLOGICAL, OR RADIOLOGICAL THREATS 21
SECURING YOUR MAIL CENTER FROM HAZARDOUS SUBSTANCES
REFERENCES 25
CHECKLISTS AND ADDITIONAL RESOURCES