We recently went through changing email passwords for one of our hosting clients through SiteWorx. They can log into the webmail or IMAP clients just fine using the new passwords, but when they try to change the Vacation Message through Horde it gives an error message indicating that the update failed and they should check the username and password and try again…
This is still an outstanding issue, but the development team is aware and there is a bug report on file. The best work around is to set the vacation message through SiteWorx as John suggested. Keep an eye on our changelog ( http://interworx.com/changelog ) or feel free to submit a ticket any time to inquire the status of the developer ticket.