Postal intercept is when a person intercepts your credit card number through the mail. Most mailboxes are not SECURE, and most thieves know this. If at all possible, it will be in your best interest to add some kind of lock to your mailbox if one is not already in existence.
If you are waiting for any cards to come via mail and you do not receive them, contact your credit card company as soon as possible. Certain companies like Airborne Express will leave your credit card on the doorstep if you are not home to receive it, and it could easily become stolen. If you believe you are a victim of this type of fraud contact the United States Postal Inspector.