NEVER.

The mail is sacred, and sacred is the trust between the Post Man and the recipients of his precious parcels. You have made a solemn pledge to deliver this letter to the doctor, just as soon as you determine where this address is, or find any sort of discernible mailing address in this wasteland, for that matter. The mail is freedom. The mail is life. The mail is the very fabric of civiliz...

Wait.

Hold that thought for one moment...