This issue occurs when your account that is in German localization sends an email that exceeds the maximum size. You receive the following non-delivery report (NDR) that reports the size limit in the kilobytes (KB) size value instead of the megabytes (MB) size value:
die maximale zulässige Nachrichtengrösse beträgt xx KB. Die forliegende Nachricht weist jedoch eine Grosse von xx KB auf.
This issue occurs because of the incorrect localization string in the Text parameter.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.