[otrs] [OTRS] To: field in responses is empty

Hi, We are having a problem with our OTRS installation. When responding to a ticket the "To:" field appears empty. Although in the original ticket its fine. Whats interesting is that if you split the ticket the "To:" field populates fine. Ive done a lot of searching through the archives and cant find anything like this. We are running 2.3.3 and Exchange. Ive also had a look in the DB and the article seems to have the correct a_from and a_to addresses. Its almost like the reply just isn't picking these up. Same also happens for CC fields (not as important). Any tips or suggestions would be more than welcome. Thanks in advance... Gordon