BTW, there are no FBI postal inspectors. FBI are the general federal police. They've got their hands so full these days with counter-terrorism activities that they've been unable to perform many other duties. Bank robberies are now remaining with local PD's robbery divisions for investigation.
In any event, Postal inspectors are series 1811 federal criminal investigators, appointed by the US Postal Service to investigate violations of the United States Code pertaining to domestic mail. I would expect their enforcement activities to continue to rise because they are expanding their ranks and are still in the midst of the largest hiring push in 20 years. The DEA has been putting trainees through Basic Agent Training (BAT) classes at Quantico on almost a monthly basis, and it is rumored that the agency will be growing by over 200 agents next fiscal year. Consider yourselves warned.
RW