You open a box, or have/pay someone to open a box for you, under a fictitious business name. Packs are signed for by the UPS employees and you just pay cash every six months or a year to keep the box. Change locations and business names occasionally.
A local pro here paid some homeless guy with an ID $50 to open a box under a made up business name using a made up address. If busted, (though he only ordered domestic) they would go to an address that didn't exist and look for someone that doesn't have an address. That would mean they would have to stake out the UPS store. Since his orders were always under a grand it would be hard to justify a stakeout. He never picked up his packs as soon as they arrived. He did get one seizure but that was for an international order which he never did again.
Here they require two forms of ID - most homeless people don't even have one form - and if you open more than two boxes at different locations (locally) within one year, they flag you and ask you for additional info on the business. (Letterhead, website, business checking account, etc.. anything to prove it actually exists). Their databases are all linked now and the same box owner info (DL, passport, car registration, etc..) that was used to open it will be shared among stores.
Keep in mind this is South Florida where it isn't just roids that people bring into the country through here. Rhino horns, illegal car parts, mj seeds, etc..
You think they won't stake out a store for a small pack? Go ask Uncle Z that. Few years ago his boy got popped when they waited for weeks for him to come to the store and pick up a pack of LABELS that came through. Yeah, no roids. No oils. No tabs. Nothing but paper labels. Last time I checked, labels (no matter what was written on them) were not illegal. But they decided that it could lead to something bigger. It did. Dude was popped here and four months later with the info they passed along, Z's bigger remailing operation overseas in Poland was netted as well by the Polish task force. But they did manually stake that store out after a week or so because the electronic tag that was put inside when it was discovered at Customs and that would indicate when the pack was opened went dead. After that they had two agents watching that store from the minute it opened until it closed for several weeks.
It isn't how much they know you have sitting in the mailbox they are interested in. It's how much they don't know you may have sitting somewhere else that they want to find out about.
But yeah, like I said you get a fall guy. Order a pack, tell the guy ahead of time that when it comes "on the inside is your stuff, you can have - this, this, this, that, some of that, et.." That way the sucker runs home and opens the pack and if there is an electronic tag inside