For OCONUS bases, the U.S. military transports all mail for their service members. Much of this mail ends up being junk or bulk mail. This consists of coupons, free magazines, advertisements, etc which the service member cannot use for the most part anyways. For certain bulk/junk mail it is shipped 1st class to members. Both of these mailing options increase cost where no real demand for these items exist.
It has been argued that receiving these items in the mail is a "Quality of Life" initiative. I and many would disagree. Receiving spam or junk mail does not contribute positively to someone's well being especially for the enormous cost.
It has been estimated that the total cost for all bulk mail government-wide would be $100M per year.
Since many do discard thesitems immediately upon arrival, it would make sense to eliminate this program altogether. (I pitched the junk mail into people's boxes and cleaned the trash and found that the junk mail had just made its way into the trash can).
The USAF had conducted a study on this in the last 3 years so this data is still available.