Changes have been made in Git (master):

commit 28793a663638a055cc01257ca7e6f2e067bb6836
Author: Jan Schneider <jan@horde.org>
Date:   Tue May 6 12:25:35 2014 +0200

     Use the event's or calendar's owner identity when sending 
notifications (Bug #13158).

  kronolith/docs/CHANGES      |    2 ++
  kronolith/lib/Kronolith.php |    5 +++--
  kronolith/package.xml       |    4 ++--
  3 files changed, 7 insertions(+), 4 deletions(-)

http://github.com/horde/horde/commit/28793a663638a055cc01257ca7e6f2e067bb6836

Please delet this request.
With more tests i saw the Status get's updated in the event in the calendar.

So, the only request for change is low-level:
  An other text after clicking the link in the invitation Mail.

Change from "No from address provided." to something with more sense 
like, "Your answer was accepted" or "event updated".

Sorry for false alarm.

Hi,
in the invitation E-Mails, when i press the link for accept, deny, 
..., the Event is not updated in the Calendar of the Organizer of the 
Event.

This situation is there for all invited Persons, which are NOT 
connected with an account on my Mailserver & are not logged in! And 
also the "Error Message" provided isn't helpful.
Message: "No from address provided."


The provided link is for example:

https://konfig.example.org/webmail/kronolith/attend.php?c=aJdjypjhjb8nsR6qJ9bKSQ1&e=mf7ZkRJeVskZVepxJBxTkQ7&u=external.user%40example.com&a=accept

the more or less type of link, which is working, is:

https://konfig.example.org/webmail/kronolith/attend.php?c=aJdjypjhjb8nsR6qJ9bKSQ1&i=20140502090843.rLBcJfSsOmALrbgfppSlwg3%40.example.org&e=mf7ZkRJeVskZVepxJBxTkQ7&u=external.user%40example.com&a=accept

The i-variable in the link is created with the "event_uid" from the database.

So, i think, there is somewhere a failure in the Linkcreating part of 
the event-creation/invitation mail.
I believe, it's first in the kronolith.php in this part:

if ($action == self::ITIP_REQUEST) {
                 $attend_link = Horde::url('attend.php', true, -1)
                     ->add(array('c' => $event->calendar,
                                 'e' => $event->id,
                                 'u' => $email));
                 $view->linkAccept    = (string)$attend_link->add('a', 
'accept');
                 $view->linkTentative = (string)$attend_link->add('a', 
'tentative');
                 $view->linkDecline   = (string)$attend_link->add('a', 
'decline');
             }
Probably there have to be:

if ($action == self::ITIP_REQUEST) {
                 $attend_link = Horde::url('attend.php', true, -1)
                     ->add(array('c' => $event->calendar,
                                 'i' => $event->uid,
                                 'e' => $event->id,
                                 'u' => $email));
                 $view->linkAccept    = (string)$attend_link->add('a', 
'accept');
                 $view->linkTentative = (string)$attend_link->add('a', 
'tentative');
                 $view->linkDecline   = (string)$attend_link->add('a', 
'decline');
             }

if there is anywhere else a need for code-change, and my thought is 
right, i don't know.

But without the i-variable the Events in the calendars don't update!

Best Regards,
ChriZ