Question

if you do not know the recipient
name how would you close the letter​

Answer 1

Explanation:

If you do not know the name of the person you are writing to, begin with Dear Sir or Dear Sir or Madam or Dear Madam and end your letter with Yours faithfully, followed by your full name and designation

Answer 2

Answer:

When you don’t know the name of the person to whom you’re writing, addressing the letter can seem daunting. If you’ve done your research and cannot locate a contact name, it’s OK to address your letter with “To whom it may concern.” While it’s always better to address your business letter to someone specific, a "to whom it may concern" letter will suffice when you don’t have a contact name available.

It would give better interactions.