He was succeeded by his nephew and adopted heir, Valerio Tamburini Montelupi (Walerian Montelupi, 1548–1613), who thus became the richest citizen in Kraków. From 1568 Montelupi was postmaster general of the Polish Royal Post (succeeding Pietro Maffon), running one public service to Vilnius (in three weeks) and another to Vienna and Venice (in ten days). These services were suspended in 1572 and when resumed in 1574 were reserved for the carriage of royal messages. In 1583 he was confirmed as royal postmaster general by the new king, Stephen Báthory, on condition he maintain public deliveries between the major cities of the Polish-Lithuanian Commonwealth, and an international service to and from Venice at least twice each month. His position enabled Montelupi to provide high-level information services for correspondents including the Medici in Florence and the Fugger in Augsburg. At Sebastiano's death the postmastership also passed to his nephew Valerio, and in time to Valerio's descendants, the last postmaster of the dynasty being Carlo Montelupi de Mari (Karol Montelupi, died 1662). Another Italian, Angelo Maria Bandinelli, then became royal postmaster general. A magnificent monument to Sebastiano Montelupi and his wife Urszula was erected in St. Mary's Basilica, Kraków. The work has been attributed to the workshop of Italian-Polish architect and sculptor Santi Gucci. A street in Kraków is named after his family, as is his kamienica, and a palace built by his descendants. In 2008 a commemorative stamp set celebrating the 450th anniversary of the Polish postal service was issued, featuring portraits of Prosper Provano and Sebastiano Montelupi. The portrait of Montelupi was based on the effigy incorporated into the Montelupi monument.