This sounds like a scam, joke, or other foolishness.
It's difficult to imagine that any government would pursue a fine that large solely by mail. And it's impossible to imagine a fine that large for a simple drone regulation violation.
Where...
First:
1. Are you sure you received that from the Spanish Government and not some sort of scam?
2. 250,000 Euros!! WHAT DID YOU DO?!!!! Fly without insurance?, Commercial without permit? attept to overthrow the Government?!
3. Do you plan on...