[horde] IMP Disposition-Notification-To seems not working.

[김 덕곤]

I'm using Horde 5.2.2 + IMP 6.2.0

When I receive a message contains 'Disposition-Notification-To'.

Horde shows

'The sender of this message is requesting notification from you when you 
have read this message.
Click here to send the notification message.'

and I click on 'here' then

'The Message Disposition Notification was sent successfully.'

But it doesn't send any notification message.