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1.
An expression used saying that mistakes are okay if they can still be corrected before a letter or package goes out the door or in the mailbox to the recipient. It refers to an office building that has a staff member who carries the mail to the mailbox. Once that person has hit the elevator, then the die is cast and the errors cannot be corrected.

Alternatively, it can be used to refer to hitting the send button and sending an e-mail that cannot be undone.
As long as it is okay when it hits the elevator. -boss

Oh man, my love letter to her is addressed to the listserver and it has already hit the elevator.
by JW July 01, 2009