First, go easy on informality. ....Affectionate terms such as “toodles” or “lots of love” do not enhance proximity to the recipient unless the closeness is already there. “Smiles” is unspeakable."
"Use proper grammar and spelling."
"Avoid being prescriptive. “Have a nice day”, “Happy Monday” or “Take it easy” emphatically do not promote relaxation."
Reading over this, it doesn't seem to give any concrete examples of what, precisely, one should close an email with. A lot of advice about what not to say, it's like we should end emails with just "End of email, Goodbye."