This is the second week of TNTina's trial, which means when you've completed 18 of her challenges, you'll be able to take part in her Loyalty Mission. To choose between its Ghost and Shadow styles, you will need to destroy the opposing group's Dropboxes. To do this you will need to know where to find them and you will also need explosives. Dropboxes really only spawn in built-up areas, so finding explosives shouldn't be too difficult.
The map above shows currently known mailbox locations, with the white pins indicating Ghost locations and black pins indicating Shadow locations. Below you'll find screenshots of each mailbox and its location, if you need more help finding them in-game.
Remember, you have to detonate two dropboxes that belong to the group you don't want to join, so if you want the Ghost skin, detonate the Shadow dropboxes, and vice versa. A little tip here, if you want to blow up two Ghost Mailboxes then head to Frenzy Farms. Yes, he tends to be a bunch of fighters and bishops, but he also has two Ghost mailboxes that are very close to each other.
Steamy Stacks
Ghost
Ombre
Pleasant park
Ghost
Ombre
Sweaty sands
Ghost
Ombre
Holly Hedges
Ghost
Ombre
Slurpy Marsh
Ghost
Ombre
Frenzy Farm
Frenzy Farm has turned out to be interesting, as we can find two different Ghost Mailboxes, but we haven't been able to find a Shadow Mailbox yet.