I searched on Google and through Wikipedia, and it appears that the email belongs to the Federal Criminal Police Office of Germany. This is their official website:
https://www.bka.de/I'm not a German citizen, can someone from outside Germany file a report?
I know what the BKA is and I know German, but that's not what I asked. My question was where on their website did he find that complaints should be sent to that email address? I have visited their site before and there is an online form that you need to fill out to file file a complaint. The form asks for all possible personal details.