@Anonymous wrote:
I too work for the Post Office as well but I dont carry mail. I actually handle the mail before it goes out to branches to be carried by the carriers. I see a lot of the CC mailers daily also, more so a lot of Discover and Amex mailers lol.
Good to know there's my postal brother/sister on this forum! 
On the delivery side, You're right I notice mostly CapOne, Discover and AmEx following by but Chase and Citi while the rest are less