Abstract: In an automatic mail processing apparatus, the mail is fed one by one by a feeding mechanism to a transport path having a stamp detecting station and a canceling station. At the former station, each piece of the mail is scanned by a pair of detectors which determine the presence or absence of a stamp at the lower end portion of both surfaces of the piece of mail. In the absence of a stamp at the particular portion, the piece of mail is switched to another transport path where it is reversed for subsequent rescanning. When the reversed piece of the mail is fed back to the transport path, the operation of the feeding mechanism is temporarily stopped to prevent the reversed piece of the mail from meeting with subsequent pieces of the mail to be fed by the mechanism.