In 1869, German missionaries established the first German presence in the territory that would become German East Africa. In 1884, the Company for German Colonization was founded by German explorer Carl Peters, and immediately began establishing treaties with local chiefs in the coastal region.

Over the next decade, the newly-founded German East Africa Company would increase German influence in the area by opening customs houses and forming agreements with local chiefs and Sultans. In the last years of the 1880s, however, Arabs opposed to the increased European presence began raiding and killing German settlers. The German East Africa Company requested assistance from the Imperial government, which quickly came in the form of ships and men under the command of newly-appointed Imperial Commissioner Hauptmann Hermann von Wissmann. Within a year, the insurrection was crushed, and in 1891, Germany acquired sovereignty over the entire territory.

A postal agency was first opened at Bagamoyo on 4 October 1890.  At the time of its opening, it was second in importance only to nearby Dar-es-Salaam, as it was a major hub between the interior and Zanzibar.  The postal agency was elevated to a post office with the formal founding of the colony in 1891.  In the following years, Bagamoyo/Bagamojo decreased in importance as Dar-es-Salaam grew, particularly as the railroads opened alternate routes into the interior.  It closed in August 1916 due to the arrival of British forces.