First the letter was posted by registered mail from the MonacoPhil-2017 International Exhibition to Zvyozdny Gorodok, the place where the Russian Cosmonaut Training Center is situated. Then the letter was delivered to the International Space Station by the Russian "Soyuz MS-08” spacecraft. To document the delivery, on board the station, the letter was marked with all proper board seals including the Russian official “Russian Post. ISS. Russian Segment” round board post mark dated 23 March 2018, the day when the “Soyuz MS-08” spacecraft docked with the ISS.