Let me correct the forum.
I am a native speaker from the USA.
In the United States, you normally write: "Best Regards,"
In the UK, you normally write: "Best regards,"
That is the difference. Americans write the word Regards with capital letter to underscore the sincerity of the wish. It is like a birthday card with the writing "Happy Birthday," instead of "Happy birthday." The latter would not look very sincere, even though it is grammatically correct.
For those puritans out there, UK English is the original variant. For those practical people out there, US English is the de-facto global standard, since the USA controls most of the technology and social platforms, tools and services of the Internet.