In the countries you are licensed in you are legally required to reply to law enforcement requests. In most places there is no official channel for this. It is literally stuff like LE@Fintech.com. Emails come from all over and random domains that appear official-ish. Most official domains do not have DKIM or SPIF setup, very easy to spoof. LE by and large do not take security seriously, they do not take data transfer seriously.

Most requests are digitally signed PDFs that come via email, require a response sent to another email.