@morrow without logs this will be hard to track down. can you ask your administrator to open up a support case for this?
A stub is a pointer left in the primairy ZCP server that points to the actual message inside the Zarafa Archiver server. When selected the message in the primairy ZCP store is "de-stubbed", which presents the user with the content that has been retrieved internally form the Zarafa Archiver server. All this without the user having to do anything special.