But this is the issue. There is not one way to do it right.

My ideal message from my telco would be this one line:

"Hi Leo, your monthly bill for <phone number> is available. Get it here: <url>"

going further i have a strong preference not to be named at all in an email from my phone company. let's keep it simple; if i want the email at all then i want to go right to the bill URL, in your example

It's your personal preference to be addressed with _Sie_, but languages change and German is seeing shift to the use of _Du_ even for transactional business [1]. Target audience, region, familiarity etc. will all affect which word is used. Claiming the use of _Du_ in customer relationships as "wholly inappropriate" again is an expression of personal preference, not fact.

[1] https://www.abendblatt.de/wirtschaft/article233949947/firmen...

Isn't personal preference the entire point, though? If the aforementioned German aunt is offended enough by how a company addresses her, she might stop doing business with them. That's a loss for the company and is something they might want to think about. (Or maybe not, but who knows.)

I have a personal preference for wearing clothes in public. I think people would rather that was respected, certainly in my case.

It got a lot more common during Covid, the social distancing rules in Supermarkets etc. were often written with the informal "Du", I guess to foster a sense of community and "we're all in this together".

Not saying she's unreasonable for feeling that way - just wondering if this is also something that should be considered in Asia, too, and giving a bit of context for people who aren't familiar with Germany. I know that Japanese has an even more "complicated" (to non-native-speakers) grammatical distinction of familiarity, but not much more about it, and have even less idea about how it works in other Asian languages/cultures.

Knowing what name to display isn't always enough - you also need to think about how the rest of the text around it should be translated to match. For German, the safe answer is still third-person plural Sie, unless you're absolutely certain your audience are all children, and missing that distinction might be taken by your audience as either that you're trying to be creepily over-familiar, or that you think they're children.

A sibling comment says that "Du" (second-person familiar) for business is becoming more common, and while that's true, I would NOT recommend using it without a good knowledge of German culture and your specific audience.

I'm not sure about older people, but business/formal emails in Japanese are like at least 70% fluff. There are loads of guides on the internet like [1], just look at the English translation of the example at the top...

Depending on the level of formality you might need to conjugate verbs slightly differently or use vocabulary that's considered more respectful. From my experience the younger generation is more relaxed about the rules, but Japan as a whole is pretty slow to change.

[1] https://www.wasabi-jpn.com/japanese-lessons/how-to-write-ema...

I'd say it depends on the area and the type of business. In Lower Bavaria it's quite common to use informal language even with strangers. Any mechanic, plumber or other craftsmen will use "Du" the moment they see you. Formal language is usually used in a more formal environment, like banks or maybe some fancy restaurant or fancy shop.

I speak both german and french, and I don't like being addressed with "Du" or "Tu", be it in letters, email or whatever. It is for me a lack of respect.

In France the etiquette requires that you ask permission to use "Tu", and there are people who refuse you the right (it basically signals that they see you as a servant).