DBMail & Horde Webmail unknown address, subject, date

Hello there ;)

I'm using Horde Webmail as a web-based frontend client for my customers.
A lot of times Horde Webmail shows the listed emails as unknown address, 
no subject and unknown date.
Once you click on an unknown email horde goes and fetches the data.

As the IMAP backend I'm using latest dbmail version 3.2.3

is there some setting ... tuining ... I can apply so dbmail works 
together with horde and shows the details of the emails in the mailbox 
listing?

thanks & greetings
Becki