International packs would get you a love letter at worst. Domestic pack leaking like that could get a call from a drama starved small town post office to the bored Postal Inspector who gets to go on a road trip with his never before used field test kit, and go fill FBI on that pack. A chance to use the whole rarely used skill set... warrant request, coordination with DEA, then when they decline to get involved, the local yokle small town sheriffs office, who'll be happy to call in the entire team for a rare black fatigues "controlled delivery" / time and a half overtime / post bust BBQ get together opportunity.