Student or Learner
I ususally use Yours Sincerely/Sincerely to end my emails.
I heard that Yours Sincerely is only used to email 1 person.
Is that right? Thanks
I have not heard that. "Sincerely", or, "Yours Sincerely", or, "Sincerely Yours", are rather formal endings. If I e-mail a friend or a peer I either use "Regards", or, "Best Regards". "Sincerely" or its other forms are generally used in legal or business matters where formality is required. This, of course, depends on your culture, as it relates to both your type of business and your ethnic background.