Government use of electronic surveillance is governed by two laws, the Omnibus Crime Control and Safe Streets Act and the Foreign Intelligence Surveillance Act. Because of traditional difficulties with the US Postal Service, some problems with mail delivery will occur, such as a machine catching an end of an envelope and tearing it, or a bag getting lost and delaying delivery. Remember that the glue on envelopes doesn't work as well when volume or bulk mailings are involved. Mail may arrive late, on a regular basis different from others in your neighborhood. Mail may never arrive.
More leeway is given for opening first class international mail.
Bureau agents were given special training in burglary, key reproduction, etc. for use in entering homes and offices. Items of obvious financial value are left untouched. Equipment vital to the organization may be broken or stolen, such as typewriters, printing machinery, and computers. Signs of a political motive are left, such as putting a membership list or a poster from an important event in an obvious place. Information about an organization or individual can also be obtined by placing an informer or infiltrator.