Mails in file repositories cannot be removed

If a mail is coming in and has matched, we store it in our own file repository to handle the content of the mail later on. If the content is NOT read, it is possible to remove the mail from the repository. After reading the content (method getContent()) the removal is impossible. It causes an exception

Exception in thread "Thread-10" java.lang.RuntimeException: Exception caught while removing an object: java.io.IOException: Unable to delete file: PathToTheJamesServer\bin..\var\mail\queue\draft\4D61696C313530323238313638303734332D62343337633939352D323963352D343862652D386638312D643066626533313232623533.Repository.FileStreamStore
at org.apache.james.repository.file.AbstractFileRepository.remove(AbstractFileRepository.java:274)
at org.apache.james.mailrepository.file.FileMailRepository.internalRemove(FileMailRepository.java:257)
at org.apache.james.mailrepository.lib.AbstractMailRepository.remove(AbstractMailRepository.java:152)
at de.desy.test.james.mailet.DraftMailetProcessor.processMailAlternate(DraftMailetProcessor.java:105)
at de.desy.test.james.mailet.DraftMailetProcessor.run(DraftMailetProcessor.java:82)
at java.lang.Thread.run(Thread.java:745)

The java process still holds a file handle to the FileStreamStore file.