Sextortion scam. Threatens to expose 'lewd images' of victim watching 'adult content' online to all their contacts. Says they hacked your OS through a Cisco router vulnerability. Usually includes a password, that may or may not be the victims', to seem more believable.
India, 2019-05-20 16:41:35
same as the other report here, tries to get you to send money to not "expose" photos (they don't have)
United States, 2019-05-29 09:18:55
Received: from P4kjJVL97 ([210.186.68.95]) by smtp.web.de (mrweb101 [213.165.67.124]) with ESMTPSA (Nemesis) id 0MQ6PP-1hZGqX1jcp-005FSy; Sat, 25 May 2019 20:58:43 +0200
Bulgaria, 2019-06-02 22:16:32