U.S. Postal Service Mail Logging aka USPS Mail cover

A USPS postal mail cover is a procedure whereby the post office receives a request from a law enforcement agency (as per Title 39, United States Code, Section 410; Title 39, Code of Federal Regulations, Section 233.3) and delivers to them photographs of the front of all letters or packages to the named recipient for up to 120 days. In emergency circumstances the request may be verbal. No judicial oversight is needed. The attorney-client relationship is respected, but not religious or medical communications. Mail covers are not intended to be introduced as evidence in criminal or civil proceedings. Reproduction of the request Form 2009 and/or attachments are prohibited. Mail cover requests for addresses at Commercial Mail Receiving Agencies (CMRA mail drop) will normally not be processed. Although the intent is to aid criminal investigations or assist in the identification of property, proceeds or assets forfeitable under law, officeholders have been known to use it illegally to spy on opposing candidates, since the procedure is conducted in secret with no oversight. Copies of affidavits of such violations are appended along with press accounts.