[otrs] TicketKey/Value not working

Hi, I'd like to transport a few values from a proprietary mailing tool into OTRS system. I think the X-OTRS-TicketKey/Value headers could help me to get the stuff into OTRS database. My problem is, that OTRS seems to ignore these headers. Nothing happens. Other X-OTRS headers like the one for setting the queue are doing their job perfectly. Any idea? Is there a configuration option (beside the watched headers listing) that could be the problem? Sample headers of a test mail: X-OTRS-TicketKey2: original-date-mssql X-OTRS-TicketValue2: 2009-09-01 08:09:06 X-OTRS-TicketKey3: original-date-unix X-OTRS-TicketValue3: 1251787566 OTRS Version is 2.4.5 Thanks for your help. - Timo