>I'm using FTPXplorer, which sends the RETR nnnnnnn command to the server, and some servers simply resume from the given offset, but this server replies that "Offset must be 0" and starts from 0. So it actually knows about the offset syntax, but doesn't allow it. It makes me particularly happy when my connection breaks after 140 minutes of download, less than one megabyte before the end ;).

True enough! Doesn't do much good if the server refuses to support it...