I sent an email to a couple of customers about a company in our industry that I heard had gotten into trouble and was shut down. I thought it was true. One of the people I emailed this message to, forwarded it the company to ask if it was true. They denied it, and now this company that I had mentioned in the email has sent me a letter, to my email address from an attorney, it states that I must send out a retraction to everyone I sent the email to and provide them with proof of this within 3 days.
Do I have to respond to a letter sent to my email address from a lawfirm?