[horde] Problem with Horde "Mailbox does not support mod-sequences"

[Luca Bertoncello]

Michael J Rubinsky <mrubinsk at horde.org> schrieb:

> You, or an admin, has disabled dovecot's mailbox indexes. This is  
> where MODSEQ values are stored.

Well, I didn't disabled anything... But it can be, that I didn't enabled
them... :)

Could you say me, HOW can I enable the mailbox indexes?

Thanks
Luca Bertoncello
(lucabert at lucabert.de)