Have a day.

You know you are fucked with kindest regards

End it “Retards” and if anyone says anything you can claim it’s a typo.

I feel seen! If you get “regards” instead of “best regards” you should know you’re on my shit list.

In German you can use “Guten Tag” as greeting when you see meet someone. When writing mail, you can also use it as greeting even if it is not that common, to use “Guten Tag” in written conversations.

BUT: When you use “Guten Tag” at the END it’s like a “Fuck off!” (regardless of written or in verbal communication) without being an insult.

I’d do the the opposite. I generally use the default “cordially”. But if someone pissed me off I’d use something overly formal and polite like “amicably thanking you for your eventual reply over the matter; if it pleases you”