Yours faithfully or Yours sincerely

Yours faithfully (to unknown person on business)
Yours truly (to slight acquaintance)
Yours very truly (ceremonious but cordial)   “Note : Ceremonious – relating or appropriate to grand and formal occasions.”
Yours sincerely (in invitations and friendly but not intimate letters)

With slight variations between British and American usage, these forms are still in use.

If you don’t know the name of the recipient.

Yours faithfully is British usage. It is used when the recipient is not addressed by name, as in a letter with a “Dear Sir” salutation.

Yours truly is the American equivalent of “yours faithfully”.

When you do know the name of the recipient.

Yours sincerely is also British. Americans tend to reverse the order and write Sincerely yours.

Which words to capitalize.

Only the first word is capitalized:

Yours faithfully,
Yours sincerely,
Sincerely yours,