Possible Clues:

• Abbr. on a letter to Iraq, since 2003
• Base address: Abbr.
• Receiver of private letters?: Abbr.
• Military mailbox, abbr
• GI's mail address
• Mount ___ (Philippine volcano)
• How to address the sgt.?
• Major mail handler?: Abbr
• Mil address
• Return address for many absentee ballots: Abbr