When to use Regards, Best regards, Kind regards in email / letter ?

When should I use Regards, Best regards or Kind regards at the end of an email or at the end of a letter ? Do these sign-offs have the same meaning in English ?

Regards, Best regards and Kind regards don't have exactly the same meaning, but there are not a big differences between them. Each of them is prefered in different situations. It depends on who is the recipient of email or letter, for example friend, customer, employer, colleague etc.

• Regards - means that you have respect for the recipient (but not a close relationship with him or her)
• Best regards - is a semiformal, friendly but respectful closing for emails or letters. It can be used for both personal and professional correspondence.
• Kind regards - is a little more formal variation of Best regards. It is appropriate to use it in business correspondence, because it is considered to be more professional.

Adjectives best or kind give to "regards" a bit different meaning, that is appropriate in some specific situations, for example in formal or semi formal communication.