Quite a few players liked it in that Limited environment. Also, a Blue/White Trading Post deck ran two copies with some success back in 2013. That was an actual thing that happened. In Commander, while hardly one of the best Equipments you can run, there are plenty of players of Jor Kadeen, the Prevailer and Kemba, Kha Regent that have run it out there. It’s a bulk rare, but as they go an Equipment that can also be a creature is never a bad thing.
When the Mail was reprinted in Magic 2015, however, it was much more mediocre in that Limited environment. It was still somewhat playable, but it wasn’t a rare anyone wanted to see. It was fine in Sealed if you didn’t have any good creatures to play… but you’d never actually want to draft it, despite being able to fit into literally any color. Whatever the case, it’s a well-designed card that was just printed in one too many Core Sets.