"""You are directed to provide records responsive to this letter electronically to the FBI within 21 business day(s) of receipt of this letter"""

I wonder how the exchange takes place? There's no mention of encrypted mail or anything just an additional note that regular mail and non-secure fax are not secure enough.

They also seem to have a template of sorts as indicated by the day(s) and the phrasing when it comes to accounting periods vs. 1st to 1st.

I wonder if you can forge (or possibly man in the middle) such a request (there's no digital signature of the letter I suppose). You'd need to set up a fake agent persona with phone number and fake signature. For a criminal organization that doesn't seem to be an unreasonable afford.