[Dovecot] Wrong dates in Outlook

Hello,

We're migrating from Ipswitch Imail to Dovecot. There seems to be a problem with Outlook after converting the emails with mb2md and whole bunch of perl scripts to correct all the idiotic mistakes that Imail has made. Outlook will display the date and time of the conversion as the date of the message, rather than using the Date: header. The same does not occur in Thunderbird or Horde/IMP. Any ideas?

Alex