search for: 2mails

Im trying to sync 2 mailserver with dsync mirror functionality. Problem occurs when mails arrive in the same folder on both sides then dsync sometimes runs into problems and duplicates that entrys on both side(2mails then with same content). After running again the same happens again(now 4 mails with same content on every side). And then duplicates this mails on both sides on every run :( Anyone with same problem or is something that could cause this? I tried dsync with and without -f option but no change....