The other day I was in the Mall in Columbia and went looking for a mailbox. I asked several merchants and though they all seemed to know about the mailbox in front of the American City Building, no one knew of any in the mall.
I don't believe there is one. If there is, I certainly couldn't find it. The closest I came was stamp machine by the entrance near LL Bean. How come the mall has a stamp machine but no mailbox?
Anyway, my search led to the discovery of a cool little website. The mailbox locator lets you simply input your zipcode and it will identify all of the mailboxes in that zipcode. Click on any of the locations and it will tell you the pick up times. It also has a Google map to help you find it.
And, incidently, mailbox locator shows no mailboxes in the mall but there is one at One Mall North.