Tails have its limits, Trump talked during the campaign about the importance of sending a courier rather than using email. https://mashable.com/2016/12/31/trump-cybersecurity-courier/
https://www.fbi.gov/about/leadership-and-structure/international-operations https://www.quora.com/Can-the-FBI-legally-operate-outside-of-the-territory-of-the-USA looks like they're at the mercy of whatever spooks we got over there
https://www.theguardian.com/us-news/2018/nov/09/konstantin-kilimnik-russia-trump-manafort-mueller Konstantin Kilimnik: elusive Russian with ties to Manafort faces fresh Mueller scrutiny New details emerge about 48-year-old said to have ties to Russian intelligence, including the use of a private jet owned by an oligarch close to Putin A Russian man who is said to have ties to Moscow’s intelligence services will be receiving renewed scrutiny from special counsel Robert Mueller’s inquiry into Russian 2016 election interference, according to former federal prosecutors. Mueller is investigating Konstantin Kilimnik with assistance from three Kilimnik associates, including Donald Trump’s former campaign chairman Paul Manafort, who mentored Kilimnik as a political operative for pro-Kremlin figures in Ukraine. Kilimnik, an elusive 48-year-old, has already been charged by Mueller with witness tampering. His most recent business partner has been charged with illegally funneling $50,000 from a wealthy Ukrainian into Trump’s inauguration fund.