Which country is that? And how would you address a person called Martina Müller in a written document? "Sehr geehrte Müller?" Or is it not a German-speaking country you're referring to?

Even "sehr geehrte Müller" already includes the gender (it would be "sehr geehrter" for a man), so if you want to avoid the whole situation, you have to go informal, and indeed, I have received a lot of emails recently which start with simply "Hallo [firstName] [lastName]" (which I guess is still more formal then only "Hallo [firstName]").

Sure, but in a more formal setting you wouldn't address somebody with "Hallo Martina". So my question is how would you avoid the Herr or Frau in a formal setting?

It turns out the people who want to be addressed by neutral gender usually don't care as much about Siezen and honorifics, so the systems I built usually just go with "Hallo" or "Moin". I even had one system which would go with "Sehr geehrte/r" for people who had chosen a title or set their language preference to "Deutsch (Sie)" and with "Moin" for everyone else.

Moin is not a good way to address your Ausländerbehörde case worker though. I'd go for the more disarming Hallöchen Popöchen.

Is it not a similar issue in the US or UK? In a formal setting, e. g. communication from a company representative to an unknown (except for the name) representative from a different company, I would be using "Dear Ms./Mr. <last name>". If that is the correct way (please let me know!) you have to commit to one of only two genders and sometimes also the last name is a guess.

You could say Dear Firstname Lastname without being off.

Even in Germany you can work around it. It's necessary for a third gender option, or when the gender is not known.

I imagine that it's not France either? French has similar greetings, with the same indecisiveness around the polite/casual pronouns. There's the added challenge of Quebec where casual pronouns are far more commonly used.

There's also the trap of "mademoiselle" which is no longer used because we no longer care about a woman's marital status. It's the same as with Fraulein.

You are right that rules might need to be made by country. The beauty of small scale solutions is that you can sweat small things like this instead of applying Silicon Valley sensibilities to the entire world.

> it can only be done if you handle each language/country split separately and the app creators have detailed cultural knowledge for each country/language.

Even this presents problems, as countries like Singapore have multiple overlapping cultures with unique naming conventions. Likewise, India encompasses many languages and even unique naming conventions within those languages.

Honestly, just do it the manual way. Have three free-form fields: "Full Name", "Preferred Name", and "Formal Address". Yes, it'll mean more typing, but it's the only way to deal with several cultures.