User blog comment:TheBlueRogue/Redeem These Promo Codes for New Emblems, Grimoire Cards and Shaders/@comment-25250760-20140916051301

The emblems and shaders actually aren't collected from the Postmaster, but from Tess Everis, the Special Orders NPC to the left of the Postmaster. Tess will always have them available for pick-up, so you can freely delete them from your inventory if you need the space for other ones.