Do not reply to an unverified threatening email or pay because of it. Contact the authority using details you found independently, and keep the message as evidence.
Fear is part of the tactic
Forged letters may use official names, seals and legal language, then set a short deadline to explain yourself or pay. An official-looking PDF, case number or signature is not proof of a genuine notice. Take the claim seriously enough to check it, but do not use the email's contact details.
Check through an official route
Find the office through an official government portal or your existing documents. Ask whether a real matter exists and how genuine notices are delivered. A real legal deadline may matter; this guide cannot assess the legal effect of a particular document. Seek individual legal advice if an actual summons or order is possible.
If you already responded
Break off contact. If you shared credentials, identity documents or money, secure the accounts and contact your bank or the relevant authority. Keep the message, replies and transaction records. Report a clearly fraudulent threat through the appropriate channels; for financial loss or concrete extortion, contact the police. There is no reason to face this alone.
Official appearance and threats are no substitute for verified communication with the authority.
Sources and further help
The linked information supports this guide. It does not imply that these organisations work with or endorse MailMigo.