To improve its mail operations, the U.S. Postal Service is turning to … wireless e-mail.

USPS this year will distribute BlackBerry handsets to 5,400 managers and “key staff” nationwide, running on AT&T’s cellular network. They’ll use the devices initially for e-mail and other unnamed wireless postal applications, and voice calls, according to an AT&T statement.

The service plans to add mobile applications and AT&T quotes USPS CTO Bob Otto describing plans to explore location-based tracking, asset and supply acquisition, IT support and video training.

The BlackBerry 8800 devices are among the thinnest built by Research in Motion, include a full QWERTY keyboard, trackball, support for voice and data, integrated Global Positioning System (GPS) and a memory card slot. The 8820 device, due to be deployed later this year at USPS, combines two wireless connections: EDGE/GPRS/GSM cellular and 802.11 Wi-Fi.

According to the USPS 2005 Annual Report, mail volumes seem to be stabilizing somewhat following gradual declines over the preceding years. The service handled just over 98 billion pieces of first-class mail in 2005, just fractionally more than in 2004. In 2001, the number was close to 104 billion. Priority Mail was up in 2005 to 887 million pieces from 849 in 2004, but well below the 1.1 billion pieces in 2001.