Best regards, Kind regards and Yours sincerely have a similar meaning, but they are a bit different, because they are used in a different situations.
Both best regards and kind regards are semi-formal
. Yours sincerely is considered to be more formal
- Best regards - is a semi-formal, but respectful closing for emails or letters. It can be used for personal or professional correspondence.
- Kind regards - is a bit more formal than best regards. In business correspondence, kind regards is a professional way how end email or letter.
- Yours sincerely - is a formal expression used for business emails or letters.