Postage stamps and postal history of Zambezia
Although Zambezia was a part of the Portuguese East Africa Colony, the Portuguese government-issued separate postage stamps for it starting in 1894, with the standard design depicting King Charles, and likewise in 1898. A provisional issue came in 1902 to reflect changed rates, then after the revolution of 1910 there were several issues overprinted "REPUBLICA".
Source: Wikipedia — Postage stamps and postal history of Zambezia (CC BY-SA 4.0)