Sent to Laura (the UK).
I bought this vintage postcard (indeed, a modern reproduction) in Tangier.
In Morocco, private and international mail started years before the public system was created. French, British, Spanish and German post offices were opened in this country since 1852.
British post offices were known by the name Morocco Agencies. In the beginning, they used their normal British stamps. But then they become under the control of Gibraltar, so they used the same stamps as in Gibraltar. The stamps were overprinted "Morocco/Agencies" since 1898.
The postcard shows the first English post office in Morocco, established in 1857. From 1872 Tangier had its own postmark. Additional offices opened in various Moroccan seaports during the 1880s, and inland in Fez (1892) and Meknes (1907). On 1st January 1907, the British Post Office took direct control of the post offices, operating them until Moroccan independence in 1956.
You can read more about Moroccan postal history here and here.