I am almost certain that the R in regards must be in lower case because it follows a conjunction and is therefore a part of the same phrase/sentence. But I've been seeing a lot of emails of late that end in "Thanks and Regards," which got me wondering.
Capitalization – “Thanks and Regards” vs “Thanks and regards”
capitalizationnounsvalediction
Best Answer
Yes, many use that way, also in "Best Regards".
But, especially if we're talking about some official/formal email, I'd suggest to write according to the normal rules of orthography.
In that case, write them like this: "Best regards", "Thanks and regards" or "Yours faithfully", etc.