FTP: Deleting files with German Umlauts

I am accessing a server (IIS) via FTP protocol with files that were formerly transferred with Frontpage. The creator of these files didn't care about special characters so the filenames contain German Umlauts.

Problem is, I can't delete these files with WinSCP (only by directly accessing the server), I always get the error message, the syntax of the filename was wrong.

I tested with all WinSCP UTF-8 settings Auto/On/Off but with no success. In the deletion command with UTF-8 off WinSCP seems to replace each Umlaut with a Question mark. When I turn UTF-8 on, some (not all) of the Umlauts are converted to two question marks in that command. Whatever, both commands fail.

Any idea?

Does it work with any other FTP client?

Good point.
Tried with WS_FTP and it also can't delete the files.
(btw. both apps are not only failing to delete but to transfer these files at all).

So your guess is a server misconfiguration?

More probably lack of support for UTF on the server.