Mail in United States postal channels may be searched only pursuant to court order, or presidential authorization. United States Postal Service regulations governing such activities must be followed.
A search of items that are being handled by individual couriers, or commercial courier companies, under circumstances in which there is a reasonable expectation of privacy, or have been sealed for deposit into postal channels, and that are discovered within properties or premises being searched, must be carried out according to unconsented FISA or FRCP Rule 41 physical search procedures.
COMPELLED DISCLOSURE OF THE CONTENTS OF STORED WIRE OR ELECTRONIC COMMUNICATIONS
Contents in “electronic storage” (e.g., unopened e-mail/voice mail) require a search warrant. See 18 U.S.C. § 2703(a). A distinction is made between the contents of communications that are in electronic storage (e.g., unopened e-mail) for less than 180 days and those in “electronic storage” for longer than 180 days, or those that are no longer in “electronic storage” ( e.g., opened e-mail). In enacting the ECPA, Congress concluded that customers may not retain a “reasonable expectation of privacy” in information sent to network providers.
However, the contents of an e-mail message that is unopened should nonetheless be protected by Fourth Amendment standards, similar to the contents of a regularly mailed letter. On the other hand, if the contents of an unopened message are kept beyond six months or stored on behalf of the customer after the e-mail has been received or opened, it should be treated the same as a business record in the hands of a third party, such as an accountant or attorney.
In that case, the government may subpoena the records from the third party without running afoul of either the Fourth or Fifth Amendment. If a search warrant is used, it may be served on the provider without notice to the customer or subscriber.
“Domestic Investigations and Operations Guide Investigative Methods and Approval Charts.” Federal Bureau of Investigation, 16 Oct. 2013. Page 405, 406