Stasi Department M workers removed enormous amounts of mail from Deutsche Post each day for inspection. Mail was identified visually based on handwriting, types of letters, or specific addresses. Surveillance of mail was technically illegal in the GDR. Still, mail was withheld on an official basis “in order to prevent attacks” by western intelligence agencies, presumably using “threats and explosives.” This led to the inspection of all incoming and outgoing mail to press agencies, embassies and consulates of NATO countries, and other western correspondence.
Unofficially, in the interest of multiple surveillance, control and censorship possibilities for the Stasi, everything possible was scrutinized, both foreign and domestic. The postal inspections contributed intelligence on GDR and foreign citizens who were suspected of spying for the west. They allowed the Stasi to filter information the citizens of the GDR were allowed to access, share, or communicate to the outside world. The Stasi intercepted undesirable books, seditious content, and other materials with the ultimate goal of preventing public protests, or other conspiratorial activities. While the goal of Department M was to return the mail collected for inspection back to Deutsche Post within a 12-hour window, many deliveries were seized and never returned. This massive operation naturally resulted in frequent delays in delivery or damage to letters or parcels, which including those that never arrived, led the public to become increasingly aware of the ongoing postal inspection.
Finally, the postal surveillance provided the Stasi with information about the mood of the population in the GDR, by examining personal communications, as well as messages sent between in companies and institutions. Reports prepared by administrators in Department M on population mood included information on economic and political sentiment and specifically targeted demographic groups (Labrenz-Weiß, 13) across specific geographic locations and social strata in the GDR in order to give the best possible assessment. For example, the following population groups are described in BStU documents
- Brandenburg: 1,000 workers each at the East coaster and the Brandenburg Steel Works, and 1,000 old and new builders
- Mecklenburg: 1,000 workers of the shipyards, 500 students and 50 teachers of the University of Rostock, and 1,000 old and new builders
- Saxony-Anhalt: 1,000 workers of the chemical industry and of Magdeburg heavy machinery construction, 800 students and 100 faculty members of the Martin Luther University Hall, and 1,000 old and new farmers in Altmark
- Saxony: 1,000 workers of the Stahlwerk Riesa as well as tradesmen / merchants, and 800 students and 100 lecturers from the University of Leipzig
- Thuringia: 1,000 workers of the Unterwellenborn steelworks, Zeiss works in Jena and tradesmen, and 800 students and 100 professors of the Jena University
- Hanna Labrenz-Weiß, Abteilung M (MfS Handbuch). Hg. BStU. Berlin 2005.