The strategic position of Samsø in the middle of Denmark has been very important for the domestic communication during a long time of the Danish history. In the beginning the Vikings used the natural harbors in the shallow water of the fiords at the eastern coast of Samsø and since then Samsø and the surrounding islands have been of great importance for the Danish military during wartime. In 1709 a hospital for treatment of the plague was opened at Kyholm, a small island east to Samsø and at the same time bastions were armed to fight the Swedish fleet. In the beginning of the 19^th century the bastions of Samsø was one of the primary Danish precautions against the British fleet and in 1813 a field post connection with Aarhus was established. In the period from 1832 to 1859 Kyholm was used as a quarantine station to avoid the serious cholera epidemics. During the war between Denmark and Preussen in 1864 ships and boats from Samsø took care of some of the illegal transports between Jutland and Seeland. Finally during World War II Samsø was used for German observation posts, but also for throw downs from the allied air plains to the Danish resistant forces. In peacetime the island has been of high importance for the Danish telegraph and the ship services.

Steamers and diesel ferries. The steamers and diesel ferries were used for the postal transport to and from Samsø. Originally the transport of mail, persons and cargo went through Brundby Balle at the eastern side of Samsø. Brundby Balle became important when the Danish Prime Minister Griffenfeld in 1674 bought Samsø and the surrounding islands. But in 1676 Griffenfeld was sentenced to imprisonment for lifetime by the king Christian V and Samsø was given to the kings mistress Sophie Amalie Moth. In 1682 she established the ferry service between Brundby Balle on Samsø and Kalundborg on Seeland. This ferry service had the rights to most of the transports to and from Samsø until a private steam ship line between Aarhus and Kalundborg was opened in 1836. The coastal steamers were allowed to bring cargo and passengers to Samsø. In 1848 the service was taken over by the Royal Danish Mail, who in 1853 started an alternative service between Korsør and Aarhus. In 1856 when the railway service from Copenhagen to Korsør was opened, the Korsør steamer service was expanded and the service between Kalundborg and Samsø was closed. In 1868 the Danish shipping company DFDS took over. DFDS also opened a new steamer service Copenhagen-Samsø-Odense, which was used for additional mail transport in a few years only. In 1875 the main service was changed back to Kalundborg-Samsø-Aarhus and in 1914 the service was taken over by the Danish Railways (DSB). This route was used for mail transport until 1962, when a small boat took care of the mail transport between Maarup on Samsø and Hou in Jutland.

Ice transports were necessary during hard winters. In ancient time agreements were made with the local fishermen, who in the years 1874, 1879, 1881, 1890 and 1895 took care of the mail service when the steamers could not force the thick ice in the Danish waters. A special chapter of the Danish postal history is the air mail services in 1922 and 1929, when temporary airmail routes were established to ensure the mail transport between Sealand og Jutland. The airmail services were used for mail to and from Samsø too. Airmail service was also used in the strong winters during World War II.

The Royal Mail on Samsø is mentioned for the first time in "Kongelige forordninger" from 1734 and in the list of Danish Post Offices "Posthusfortegnelsen" from 1833 Samsø in stated as a minor office. The ferrymen in Brundby Balle handled the mail. The last ferryman was Theodor Didrik Beissenherz, who in 1852 got employed by the Danish Royal Mail. In 1860 Beissenherz and the post office moved to Kolby on the western side of Samsø. In 1889 Kolby was changed to a major postal office. From 1861 to 1884 the first mail collectors offices "brevsamlingssteder" were opened: In Besser (1861), Nordby (1863), Onsbjerg (1878) and Tranebjerg (1884). The post diligence and mail delivery by walking postmen started on Samsø in 1887. Until then the mail recipient had to pick up his own mail at the post office. The automobile came to Samsø in 1920 which had a major impact on the postal service with new offices and routes. The last local post office was opened in Ballen in 1950. But in the 1960's and 70's the local offices closed due to reorganization of the Royal Mail: Pillemark (1966), Brundby (1970), Onsbjerg (1971), Kolby Kås (1975), Ballen (1976) and Besser (1982). The post offices are still open in Nordby and Tranebjerg. On the 28^th May 1990 the zip code of Samsø was changed from 8791 to 8305, and the official name of the postal district was changed (back) to Samsø.