I'd send a copy of this email to the SOS in which his company is registered. I'd reply with a due date for your money.
No need to apologize to get what you've already earned (obviously this guy is delusional). If he doesn't pay you, by your final due date, then I'd report him to the appropriate authorities.
This email is clearly blackmail, and you shouldn't have to apologize in order for you to receive what you've earned. |