Das ist empörend: Microsoft slams umlaut for email depth charge
Found on The Register on Monday, 22 August 2016
If users include the two-dot umlaut in their email password, the system won't authenticate them and their IMAP account will refuse access.
Microsoft has warned that the issue could result if any Unicode character is used, but it cites three examples that point to a distinctly anti-German bias: ä, ö and ü.
It's 2016. Character encodings are a non-issue these days when you do it correctly; but then, MS cannot even get it right on their command prompt. Every new bug gets more embarrassing for Redmond.