In czarist times, Kybartai had a major transit post office (as Kibarty) servicing international postal traffic by rail but none during the German occupation, as a civilian post office was located at Eydtkuhnen just across the East Prussian border.
The first Lithuanian postmaster at Kybartai was Otto Kochanauskas, mandated as of January 15, 1919, though it is not clear when the post office did in fact open for business. He was replaced by Juozas Markevičius on August 7 of the same year and stayed on as deputy. With increase of staff came Antanas Aušrotas as deputy on April 1, 1920, followed by Kazimieras Venclovas as postmaster (?).
As an early post office Kybartai was provided with the Second Vilnius Issue and probably the First Vilnius Issue as well. It did have First Kaunas and possibly some values of the other Kaunas Issues, certainly followed by Fourth Berlin etc. Surviving items show that the Kybartai post office was frequented by collectors who may have brought along stamps or values not available at Kybartai. One of the customers was Max Spiekien who kept sending cards and covers to his wife Gertrud in Eydtkuhnen, and to some others – and so unwittingly facilitated a reconstruction of the evolution of postmarking at Kybartai.
In the absence of a postmarker, for cancelling Kybartai at first made do with two pen strokes producing a diagonal cross.