Email customs
Signs you’re dealing with an American lawyer: mixed punctuation (use of commas or colons in conjunction with salutations and commas with valedictions, letters in abbreviations separated by periods); use of “Best”, “Best regards”, “Sincerely”, “Yours truly” as valedictions.
Signs you’re dealing with a British/ANZ lawyer: open punctuation (no commas used after salutations and valedictions, abbreviations don’t have fullstops); use of “Regards”, “Kind regards”, and “Yours sincerely/faithfully” as valedictions.
However, the choice of valediction is more indicative than the punctuation style used.